Well there is also the UKs push for age verification to access porn online via some form of identification (and to a lesser extent when they banned a bunch of sex acts from being performed in pornography created within the country a few years back).
I wouldn't say it is directly connected, but some of the leftwing have contributed towards the environment to censor such content (be it for perceived evils or for public image), and certainly, the traditional right is fine with restricting such things as well.
Relating back to the Loli stuff, we had GAB do a site-wide ban on Lolis, with the announcement post subsequently getting spammed with lolis for a straight week until the site got ironically knocked off the web because people overreacted that a shooter had an account on the sight. That sparked a little conversation online in some places.
Japan aside (because it is going to do its own thing), in the west lolicon is illegal in quite a few countries (mainly European nanny states), and some outlets fine with most porn do ban such content (again, be it for perceived evils or for public image), though it is admittedly applied somewhat inconsistently (and pornhub being one of the biggest providers doesn't seem to care at all).
I hear many of the Tumblr artists are moving over to Newgrounds because that somehow still exists, but they are not found of Loli themselves.
Regardless I didnt see Tumblr having much going for it beyond being a place where degenerates shared porn. It might live on with the other communities that exist there but the attempt to appeal more broadly by banning porn will probably not work out for them I think, other platforms are just simply better.