The fact that they market Xamarin/MAUI as cross platform and Blazer for web, and not use any of their tech to build a cross platform native/web app is laughable.
Blazor is very new & was considered experimental until recently. It's still fairly bleeding edge.
Microsoft started Teams in 2016 & bought Xamarin in 2016.
JavaScript developers are also more plentiful than Xamarin I assume.
They should choose the best tools for the job, even if it's not there own.
- Edit - It looks like WebView2 is a Microsoft thing based on their Chromium browser version. Super common for Microsoft to make multiple competing products that do similar things.
I think Microsoft is trying to move towards a cross platform for everything from what I've seen. They have a ton of legacy stuff though.