If Tumblr had dealt with the issue of unbridled porn blogs years ago, instead of allowing the spam to become what it is because of the profit they got from it, they likely wouldn't have fallen into such a dire situation in the first place. But it's only the tip of the iceberg, really. The lack of interest (or inability due to the limits of their algorithm) to deal with the child porn situation, something that's been an issue ever since I left many a moon ago, was always gonna do them over. The lack of interest (not an inability, this was within their power) to deal with Neo-Nazi propaganda floating around the place is a similar reason why Tumblr doomed itself ages ago.
It's not a good thing to outright remove NSFW content - it's a repetition of the foolish practice of corporations to understand content production and how delivery of said content works.
- Site grows.
- Site gets bought out by large corporation.
- Large corporation finds elements of site that are unfriendly to advertisers.
- Large corporation begins purge of said element under the belief that new users will replace the ones that were lost, with all the same ideals that made said site worth buying, just not with undesirable content.
- Said tactic fails not only due to user pushback, but due to large corporation fundamentally misunderstanding what users want.
- Site begins decline as users that were essential for the site's success begin exodus of varying speeds.
- Site folds or is sold off for the process to begin anew.
In this case, Yahoo has decided that in order to regain faith with advertisers, it has to go through with what it had always wanted to do, as puritan behaviour always finds its way to the top of these businesses - purging NSFW content. But it needed a reason, as purging such content out of the blue would doom the site. But simultaneously, NSFW material was all that kept the site on its feet, due to the profit involved in hosting the legion of porn bots and encouraging NSFW material. Kind of an odd situation. But it's all come to a head with Apple and co forcing Tumblr to act - however, nothing it will do will ever be satisfactory, because not only has it murdered its sole remaining point of relevance, advertisers still wont touch the place with a pole due to 'Tumblr' and 'child porn' now being in mainstream headlines instead of the long-stirring complaints by users. Combined with a long history of site mismanagement and outright neglect for the tech aspect of things, along with allowing users to be preyed on in all manners (physical, moral, sexual) for profit, Tumblr's eventual fall was transparently obvious.
The hellsite doomed itself.