Tumblr did a porn purge after entitled Tumblrinas decided they had the right to post self-made child porn to the site via shit like showing up at LGBTP communities and posting nude selfies and bragging about tricking adult men and women into hookups, and if anyone complained or told them to get the fuck out of 18+ areas they were being evil oppressors and whatnot. This all stems from the mindset that started in the "lifter" community on Tumblr where upper-middle class Tumblrinas decided they had the right -- nay, the DUTY -- to steal thousands of dollars of clothes and makeup and brag about it while posting photographic evidence, and if you called them fuckheads or reported them to the police they screeched harassment.
There were also "underage Sex Workers" -- Mini-Thots advertising prostitution services and selling "Premium Private Snapchat Packs" aka Self Made Child Porn -- on the site, which FOSTA/SESTA specifically made sites like Tumblr liable for. All that talk about "Sex Workers" and how "LGBT people were being hurt by this?" A lot of that shit was pedos raging that this shit was being cracked down on.
(Worse, Tumblr's porn bots would auto-download the self made Child Porn and repost it. Worse Worse, Tumblr itself would "suggest" images on the left / right hand side of blogs, so if you went to a normal porn blog -- the only reason to use Tumblr -- you might get a bunch of Child Porn thumbnails without asking. Oh, and most of these bots and shit moved to Reddit in the past few months, so good luck if you're surfing reddit for free titties. Make sure you run CCleaner with a 3 pass secure wipe.)
Didn't help that Tumblr has had 0 moderation for the past 10 years, which is why shit like "callout blogs" and the like -- aka, cyberstalking and harassment blogs -- were never stopped. CNET picked up the story, asked Apple and Google WTF, Apple pulled their app, Tumblr's lawyers realized that they were in deep fucking shit, and welp.
They ONLY banned nude photos and a few other things, which is the same shit banned on DA + photographic nudity, but 4chan discovered Tumblr was just auto-blocking anything adult that got enough reports on it and someone set up a bot to mass flag weeb art and shit, so they all fled the site in a huffy rage because how dare Tumblr tell children they can't commit felonies?! REEE.
This is actually related to the Weeb Wars, because the Vic callout shit started on Livejournal and Tumblr, and only spread to Twitter after Tumblr lost so many users they weren't getting the asspats and attention they were addicted to.