Tumblr has the resources and technical capability to detect and remove illegal content quickly, and the resources to identify adult content in general. I firmly believe that the issue is in monetizing the adult content, which Yahoo, Oath, and Verizon did not seem to want to do. By removing it, you don't have to host it anymore, and a greater proportion of your traffic is monetized.
>I firmly believe that the issue is in monetizing the adult content, which Yahoo, Oath, and Verizon did not seem to want to do
Working in the adult content space will get your business blacklisted from mainstream content. No one is going to have official relationships or work on exclusive deals for your platform if their content is going to be side by side with pornography, or even perceived to be alongside it.