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.
Microsoft also supported Angular early on as it was one of the largest early adopters driving folks to Typescript.