Mearls has stated that the 4e Red Box had good uptake, but there was limited retention and purchase of further products.
You have the OSR craze heating up, and you put out a boxed set with the art from an 80s basic set, but the stuff you put inside it is pretty nearly completely alien to the D&D of that era. So, sure, it flys off the shelves - and into the wastebin. Conversely, while not that many brand new players might have snapped it up, those I saw actually try the game for the first time in the Essentials period picked it up very easily. So you had a product that was better at attracting old players, but better at retaining new ones. At the time, it must have seemed like a brilliant compromise.
Part of the rationale of 5e was to make the "on-ramp" easier. A number of people in this thread have stated that they find the "wall of books" to be a barrier across the on-ramp. That seems plausible to me.
I can see how that affects the perception of the 'on ramp' before you start playing. The learning curve 5e presents a returning player is pretty smooth, too, it's different - but familiar. A new-to-gaming player confronted with 5e, OTOH, doesn't do so well. The players I've introduced to 5e who admit to having played D&D before, even if it was only a few times, 15+ years ago, seem to pick it up fairly well, they come back for a few sessions, at least. The new-to-gaming players, OTOH, I've yet to see one return. 4e & Essentials, it was the exact opposite. Returning players would give up on it fairly quickly, new ones would get into it surprisingly often. I say 'surprisingly' because I've introduced a lot of people to D&D in the last 35 years, and for most of that time, the most common response was try it once, never be seen again. 5e is back to that familiar pattern.
Thing is, I don't think it matters. There weren't /more/ new-to-gaming players showing up in the 4e & Essentials years, just more staying with it, but it'd take 20 years for that to add up to something. Conversely, there are so many played-a-while-in-the-80s folks that might yet return to the hobby, retaining them actually means something.
I've never played a computer game or MMO, but I've played 4e more than once. 4e seems to me to be built to appeal to game players, including people who care about the game (ie rules and mechanics) elements of RPGs, and the way those elements drive play. 4e isn't built to appeal to those who like the GM to play the predominant and mechanics-independent role in determining how a game unfolds.
Yeah. I've never gotten the point of making a complex rules system for players & GMs who actually just want to freestyle RP. Yet the idea had real traction in the industry in the late 90s - WWGS espoused the philosophy ("bad rules make good games") and was successful, for a while.
I guess if you have a group that doesn't want to embrace freestyle, and you present them with a system so bad that, at every turn, their best choice is to avoid using it, they'll start to see the moments when the game slips into freestyle RP mode as the best bits....
At some point, though, the publisher runs the risk of the players realizing they don't need to buy anything... ;P