In the Tumblr ban threads, people mentioned that all of these companies should simply make their progressive web apps and give the finger to the puritan idiots calling these decisions. I agree. The questions, however, are: how much growth can be achieved without play store/ios app? Is it viable? If yes, how? Can art be more important for a site (and it's investors), than immediate, quick growth?
Tumblr was sharing images of child sexual abuse, not just regular porn. It's only when they discovered the images of child sexual abuse that they took action. They'd left user generated porn content alone for many years. That's not "puritan idiots", that's people who are aware of the harm caused by the distribution of images of child sexual abuse to the survivors of that abuse and to their business from law enforceme…
A good amount of advertisers don't like porn, so you can't monetize Tumblr as effective. Tumblr's investors want a return on investment, and the former approach allowing any legally permitted content didn't work for them, so they resorted to this. They surely did their research, and are betting that the ban on erotic material is the most effective way of increasing the revenue of Tumblr.