You said Snap is a similar but alternative to Flatpak, implying that it was developed in response to Flatpak, which simply isn’t the case.

Snap predates Flatpak, and it’s clearly a big money maker for Canonical with their commercial customers who want things like confined but upgradable services in an airgapped environment. By the time Flatpak was making enough headway to be considered feasible to use, snaps were already pretty widely used and had several fairly big names like JetBrains, ROS and CircleCI publishing on snapcraft.io.

Flatpak cannot and was never intended to do all the things snap can, such as setting up system services or distributing kernels. So even if the assertion that snaps for desktop apps were a response to Flatpak were true (it’s not), it doesn’t make sense for Canonical to stop developing snap regardless, as desktop apps are only a tiny part of what snaps do.