AbdulAlhazred
Legend
However, nothing can change the nature of the established fanbase, one segment was still chafing against 3e for not being enough like the TSR era, so the OSR would have happened anyway, even had there been no 4e, and the current come-back would still demand a more traditional, DM-focused, system for the 40th-aniversary edition.
The OSR happened long before 4e became a thing, and wasn't a reaction to it. Honestly I think 'OSR' is overrated anyway as a market force. I have yet to encounter people that actually are in any sense militant about, or even prefer, to play such games. Beyond that there was ALWAYS a certain core of people who thought the 3 1974 LBBs were the last word in RPG design. The term 'Grognard' is NOT new, it was current in at least the 90's and probably the 80's. Anyway, I was playing since the mid 70's and I can tell you that the day 1e hit the shelves there were people who hated on it.
So I don't think OSR actually matters. I don't think it appreciably shaped 5e as a distinct movement (maybe the structure of a few options was tweaked to make a more old school type of play a little easier, but 5e is hardly catering to OSR fans anyway).
Frankly I think 3.x just wasn't dead yet, and WotC tried to put a stake in it, and the beast just wasn't going to go down. It was also a sort of natural down cycle of D&D, much like the late 80's and the late 90's (note the roughly 10 year cycle). 3.x was getting long in the tooth, but not THAT long. Paizo was created by WotC basically, and it bit them. The market shrank, 'old Coke' was still able to capture almost 50% of it given the marketing and business mistakes that were made, etc. A lack of desire on the part of a decent chunk of people to move on from a game they weren't tired of (but had already bought all their books for) was a big thing, but WotC both created and walked into their own perfect storm.