[toilari]

Disclaimer: this is just guesswork from my own experiences. I do not actually have experience in running the community of a FOSS project.

I'd guess its lowering the barrier of entry by providing a "casual" platform for communication. Discord is widespread enough for many people to already have an account. Joining new servers is dead simple.

Also, collaborator retention could be another thing. I'd argue it is easier to keep less active contributors hang along when you have this sort of "community" where people do other, unrelated stuff (post memes and discuss unrelated topics) alongside the actual work on the project.