Because Bedrock runs on phones, tablets, consoles, and a host of other random crap, and does so relatively well. Because of that the install base and playtime especially among younger players is actually massively skewed toward Bedrock being the more used. Add to that rumors that the Java codebase at least was a terrible mess, and the performance issues Java edition still has to this day and it’s no wonder they wanted to do a full rewrite, especially after having to make things like the console editions and even one for the 3DS.
The windows launcher is annoying though.
Because Bedrock runs on phones, tablets, consoles, and a host of other random crap
And it also removes Linux support. Typical Microsoft.