It is history not the lack of will. At one point the windows division was in shambles (remember vista) and WPF pops up. At another point, the windows and dev division have no answers to the office group (because you know who uses non win tech) so they went react. And then external devs screamed: where is the .net cross platform story so Microsoft acquired xamarin and later form Maui out of it.
It is history not lack of trust. But the outcome is the same: lackluster support for all UI toolkits.