From what I can see it mostly does ease of development better; it’s a completely new and rather lean codebase, and it’s seen as an investment in compatibility with graphical applications.

Also, it has lock screens. X cannot do lock screens; it can have an app being full screen and pray to some collection of deities that nothing will come in front of it or that the fake lock screen won’t draw far too small, but it cannot natively do secure lockscreens that are guaranteed to work.
So there, it does something much better: security.