The business decision Apple made to largely ignore Cocoa, especially any semblance of documentation, and then confuse “native developers” by giving them conflicting half-baked solutions like Catalyst and SwiftUI? I guess given the option between a closed-source half-assed framework like Catalyst that even Apple themselves can’t make reasonable apps with (see Apple News), and an open source half-assed framework like Electron where you can at least contribute a fix instead of having to wait a full year for the surprise of whether your reported issue got fixed or not, most people just preferred the latter.