It was all after Snowdens leaks. Mozilla promised to de-fork Tor browser, move Tor into private browsing. They kept repeating this for years and years.

They even started a bunch of Tor nodes to collect some metrics. It looks like they are removing their blog posts about it

https://blog.mozilla.org/it/2015/01/28/deploying-tor-relays/

https://web.archive.org/web/20150722100146/https://blog.mozi...

> Our primary goal is to un-fork the Tor Browser

https://bugzilla.mozilla.org/show_bug.cgi?id=1173199#c31

They were very vocal about how web is broken, needs more Tor and IPFS for everything to allow more free speech for disadvantage. Today they promote unregulated censorship, banning and shadow-banning public channels. You will find many posts about it between 2014 and 2018.