I think that's a good part of it, to be honest. Plus I think also helps that Bluesky's handles look visually less confusing and unusual than the conventional double @ sign for the fediverse
@user.bsky.social vs @user@bsky.social
Plus other things like having starter packs











It's actually more so the other way around. The backend (PDS and relays) is open source but I believe the AppView is not currently open source
https://github.com/bluesky-social/pds
https://github.com/bluesky-social/indigo
https://github.com/bluesky-social/jetstream