Was there some other reason distros switched to Wayland? I've always heard X11 was just not maintained well and had too much tech debt, not so much about the security.

From what I remember, Wayland is a thinner layer than X11, basically handing clients pointers to shared buffers for them to write into, which seems better than X11's server approach. Thought maybe people were eager to switch for latency reasons, but this benchmark is showing otherwise. And would think Wayland is more efficient too, but I haven't noticed or heard of a difference.