Even if the number of vegans has not changed, the consumption of meat substitutes has increased. Also, if you remember like 10 years ago, most grocery stores had half an aisle devoted to these kinds of products and now they take up much more space and are fully integrated. Beyond specifically requests that their products are stocked alongside meat-based burgers; Just Mayo is integrated with all the other Mayo’s (and Hellman’s now makes a vegan mayo) - it’s simple economics.
I think social media outrage is as obnoxious as the next guy, but it would be wrong to say that corporate execs give a shit about some halfwit on Twitter more than their bottom line.
Finally, regarding “hipsters” and “whiny liberals” - consider that Burger King is testing its vegan whopper in St. Louis, Alabama, Georgia - not exactly bastions of hipster liberals. It did so astoundingly well that they are going to roll it out nationwide by the end of the year.
Just because a lot of whiny liberal hipster SJW whatever you want to call them type of people happen to be vegan does not place them at the root cause of modern veganism. It’s been on an uptick since before the social media phenomenon (or plague) took off, and it’s wrong to conflate the two.