Comment by pjc50

> What problem it exactly went out to solve? Did Microsoft want developers to be able to run their applications everywhere too? Absolutely not.

So .. initially it was "Microsoft Java", a managed language with tight integration into the Windows APIs, and non-portable. That was .NET Framework. A while ago they realized that even Microsoft didn't want to be tied to one platform, and moved to the cross-platform ".NET Core". It now occupies a similar role to Java but is IMO nicer.