Usenet failed, for me, due to a combination of (ISPs include any 3rd party feed providers): 1) volume of the feed (meaning ISPs were finding it harder and harder to maintain an adequate copy due to the size) leading to fewer feeds being available for users. Initially just alt.binaries.* got omitted due to size, but that grew due to point 2. 2) moderation/spam/copyright issues: most of Usenet was unmoderated and spammers found it more efficient than email to send out their messages leading to many groups being overrun. The lack of moderation also lead to groups being "repurposed" by people wanting to spread copyrighted material leading to lots of groups being blocked and then ISPs going "We can't keep manually removing messages blocking individual groups, so we are blocking all alt.* for starters..." 3) ISPs took very little action against USENET spammers themselves leading to posts from their subscribers being dropped by various other ISPs without knowledge of the drop being visible either to the poster or the ISPs customers 4) The factors above leading to USENET getting more splintered: you might not be able to see the groups you want, conversations may happen without you being aware due to the filtering. This lead to fewer consistent users especially with the rise of the web with specialist "low-spam" (at the time) moderatable bulletin/message boards acting as a "pull factor". 5) The cost/effort vs customer demand for ISPs meant more incentive to just stop offering the service pushing the few remaining consumers towards 3rd party providers (many of which were run on a low cost/fee basis which attracted spammers leading to higher costs for that provider and then being blocked: so they discontinued offerings). 6) The user experience of USENET, even at its peak, wasn't beginner friendly (those people complaining about picking a Mastodon server being anti-newbie friendly would have big issues with getting started on USENET) meaning there wasn't the takeup of new users to replace those leaving. Just my 6 cents! (and me regretting reading this post on mobile and replying via mobile!)