The architecture concepts behind Angular are very .net-esque in a lot of ways. It's often an easier transition for folks used to MVC style projects with a heavy reliance on dependency injection to wrap their head around Angular than some other SPA options out there so the two get related in this way a lot.
Microsoft also supported Angular early on as it was one of the largest early adopters driving folks to Typescript.
Angular is the framework of choice for most Java/.NET shops, because it is basically JEE/Spring/WebForms/MVC, but in JavaScript, besides being written in TypeScript which is quite appealing.
Before Angular, those developers would probably have chosen Knockout.js instead.
Is ms invested in Angular?
It's a Google project, isn't it? Is it first-party in dot.net? I though that was Blazor?