To add, Tumblr was lambasted for them not properly policing their porn[0], accidentally allowing CSAM, and Apple being the one to inform them of this error. it's what led to them banning all 18+ content, arguably sealing the platform's fate of irrelevancy.
I thought Yahoo's acquisition was what stopped their 18+ content
But perhaps the most catastrophic misfire of all was the notorious ‘porn ban’ that came into place on December 17, 2018 – a policy partly driven by a US law [1] that made websites liable for sex trafficking that might take place on their platform. The ban covers ‘female presenting nipples’, genitals, and any depicted sex acts. Until then, the platform had remained a refuge for a devoted community of users, but this decision affected swift and dire consequences.
But perhaps the most catastrophic misfire of all was the notorious ‘porn ban’ that came into place on December 17, 2018 – a policy partly driven by a US law [1] that made websites liable for sex trafficking that might take place on their platform. The ban covers ‘female presenting nipples’, genitals, and any depicted sex acts. Until then, the platform had remained a refuge for a devoted community of users, but this decision affected swift and dire consequences.
https://www.wired.com/story/tumblr-sold-to-wordpress/
[1] https://en.wikipedia.org/wiki/FOSTA-SESTA