[blandflakes]

I think realistically we're looking at a lot of causes (which is not surprising; it's rarely a singular thing). Scala 3's momentum may have already been negative but how Scala 3 landed represented a nail in the coffin for a lot of individuals, teams, and organizations.

[hocuspocus]

Scala 3 really landed at a bad time as the hype behind Spark, Akka, Play had already weaned off. Typesafe was struggling financially, and didn't back Scala 3 then (that went to VirtusLab).

Typelevel and ZIO really put a lot of effort to release many libraries on day 1 despite the hurdles with the 3.0 release, because these communities are alive and healthy. Yet Odersky is on a small crusade against monadic effect systems, which discouraged a lot of good people. On top of that there are neverending feuds and US politics...