As the title says. Note that this is just my opinion but I don't think I am to far wrong. By most accounts 5E has been a big hit and while some people might get a bit carried away with how popular it is out of the 7 D&D's it has probably outsold 4 of them being in 3rd place and it might be on track to beat the top 2. While we can't definitively say that it has not beaten them Mearls has been quite vocal about 5E beating say 3E and 2E in sales so I assume he would have said something it it beat 1E or BECMI.
So its a popular edition but why. Well I think the following reasons apply.
1. Its a genuinely good edition. Very simple reason 5E is not perfect by any means and there are some things in it I do not like but they are more annoyances than reasons that would go make me play something else. This means its basically a popular edition already. It has been 18 years since the last time D&D had a popular edition as 3.5 was less popular than 3.0 and well 4E happened.
2. Its simple. At least for a D&D edition there are a lot less moving parts with only the ASI's on most classes to worry about with spellcasters being a bit more complicated. When the 5E Warlock is about the most complicated class in the book its not that hard. 5E has seen an influx of newer players and less complicated/mass market generally sells more than hardcore stuff- think Tetris, Mario, G and PG movies vs R etc.
3. Deep Amazon/online discounts. Pathfinder for example used to be cheap as you got the PHB and DMG for less than both of those books individually compared with say 4E.. Xbox 360 was cheaper than the PS3 (and took huge market share vs previous generation), PS4 is cheaper than Xbox One. Price points are great for consumers and with recent sales of $20 you are getting the PHB at 1989 prices. If you are an American these are great prices, here in 1995 a PHB was $45 (31 USD approx), a 5E one is $75 (52 USD aprox). If I was american I would have more than 2 copies. One thing I have noticed over several groups is most players now have their own PHB vs the 2 maybe 3 a group would have in previous editions.
4. The rise of social media. Well twitter and Youtube are now a thing. These did not exist when 3.5 landed and were in their infancy when 4E landed. 5E is the 1st D&D that is popular to land when these have been mature mainstream technologies. Throw in facebook. In ye good ol days finding players may have been hard, now you can go to facebook and join a D&D group and let people know you want players.
5. Virtual able Tops (VTT's). These have been around in some form for a while but have become a lot more mainstream in recent years. Can't find a group to play? Live in a small town? Well go online and play. Also solve the decades long smelly player problem.
So that is basically it. Its easier and cheaper to play than ever, easier to promote the game than ever combined with a genuinely good edition that is popular to the extent we have not seen since 2000 if not the early 80's. Its a perfect storm of convergent technology, price, a good edition harnessed to the power of social media.
I think it's a few things, some of which have little to do with the game.
1 and 2. The design is elegant and simple, yes, but I think the real win is that it seems to have a feel that makes players of any earlier edition feel at home. Perhaps 4e players are the least served by this, but to me it feels very much like AD&D, but I think that the number of 3e and Pathfinder players that have switched seem to feel that it has a very 3.5e feel without the problems. I will also point out that I think that 4e was quite popular with new players, but didn't bring in many of the players of older editions (particularly 3.5e). While I ultimately didn't care for 4e for a variety of reasons myself, I think we should still give credit to a well designed game. I really don't think new sales suffered significantly, but that existing players just didn't embrace it. The game is also designed to play in smaller chunks. While I personally miss the 12-hour gaming sessions, 2-4 hours sessions are much more reasonable for most. 3.5e and 4e were definitely on the longer session track, provided you wanted to get through more than a couple of major combats.
So new players can easily pick it up, but the bigger win has been bringing in more players from earlier editions. Existing players are your best advertisements, there is no better way to get somebody hooked on the game than to play it. Just hearing about it and seeing it in the store, or reading the free basic rules is one thing, but not the same as actually playing it.
3. Discounts are great, but only in reference to a similar product as you point out (Xbox vs PSx, etc.). I don't think that really exists for D&D. Yes Pathfinder is big, but existing Pathfinder players wouldn't have had any reason to consider the cost, since they already owned the materials. Plus, the basic D&D rules are free. And that's great, but I don't think it's driving it either. However, I do think that they really figured out their branding and marketing strategy. While many have complained about the volume of materials being released, I think that's a small part of the D&D community. They've shifted to a similar model as MtG (big surprise), with basically two "events' annually. They have a new AP, a dozen AL adventures, video game updates, and 3rd party accessories, all coming at a sustainable rate. While I'll probably never run the APs, I have them all and steal material from them. But for casual players, it's very much like a video game approach. Pick up the AP, play through it, and 6 months later pick up the next one.
4. While social media may help, I think the bigger aspect is simply that D&D (and "geek culture") is cool now. We've had a generation grow up on video games now, and this is an easy transition. More importantly, I think you have a lot of people coming back to it and teaching their kids too. I really think that this has made a huge impact on the popularity and sale of the game. Those of us that played in the '70s or '80s to 10 year olds. In addition, D&D is really no longer geek culture. It has really become mainstream.
I don't think Twitter and Facebook are real drivers, but services like YouTube and Twitch are. Again, the game is benefiting from video gamers, who already have a culture of watching others play games. So being able to watch others play D&D
does have an impact because they can see how fun it is, and learn a bit how it's played.
5. VTT have been around for a while, but they continue to make gaming possible for friends scattered geographically. I think the bigger plus here is back to their marketing. The licensing has been great, allowing the entire library to be available on several VTT platforms. Not only is this another source of income for WotC, but having it available greatly increases the appeal of the VTT. So I'd say this is the opposite - it's been a much bigger benefit for the VTT platforms than it has for D&D.
