Other projects in the Scala world are already out there. I used the whole Akka shebang at my previous job (streams, persistence, cluster sharding, ...) and I would argue most people don't need that. It encourages over-engineering and you can usually do the same thing with simpler libraries.

Now, Akka came out at the right time and deserved to get popular. It's built on a solid and battle-tested foundation and there is a real community-driven ecosystem around it, or at least there was. It totally made sense. Also Lightbend was on a seemingly good trajectory, and Akka looked like a safe bet.

I guarantee there are small teams out there, at big companies making well over $25m, who are probably overstretched already and now need to plan an unexpected migration. I love Scala but the maintenance burden is real.

I would say it helped with early adoption. But at this point, it's got quite a bit of adoption. It's proven and for companies making over $25 million a year a proven piece of tech is generally more likely to be used than an unproven one.