Not everything is about people's dislike of 4E. There just isn't a big gaping hole in the archetypes that the warlord fills that hasn't already been subsumed into other classes.
Again, the warlord placed higher in class popularity polls during Next than a number of classes that made it into the 5e PH. There are, indeed, gaping holes in the range of archetypes playable in 5e. It'd take more than the Warlord to fill them. It'd take, well,
class balance.
And we saw what happened the last time D&D tried implementing class a balance.
Windows was, and continues to be, the market leader for the consumer computer market because there are very few alternatives
The alternatives to D&D for the prospective new player just thinking about getting into it, are very few, indeed, because no other TTRPG has meaningful name recognition outside the hobby. People come to the hobby through D&D, if they don't like D&D, they most likely never get as far as the rest of the hobby, but they probably did, at least, buy a PH. That was true in the 80s fad, almost all of the intervening years (for a bit in the 90s it looked like between M:tG and TSR's mismanagement, D&D would be gone, and Storyteller, most likely, might have replaced it, making LARPs & Vampire-fandom crossover the main source of new players.

What a freaky, Dark, world of TTRPGs that'd've been.

The current come-back is being led by D&D, because D&D was the fad in the 80s.