Citation needed, and number of users is more important than number of apps. Snaps are pushed strongly by Canonical and they actually pay people to port apps to their store, which is pretty much used by Ubuntu users only, while every other distro uses Flatpak.

Snaps are not gonna last long, like many other Canonical-only efforts. Nobody is interested in adopting them, for good reasons. Flatpak, with their shortcomings, are more flexible, actively developed by multiple entities and adopted by more people.