Microsoft might seem to be an "open source champion" now, but remember that it is a publicly traded corporation with a fiduciary responsibility to maximize profits for its shareholders and a history of anti-competitive, anti-consumer practices.
Right now they are being warm and fuzzy to regain the developer mind-share they have lost over the past couple decades to open-source software. If they get a large percentage of developers using their tools and services (looking at you GitHub) I would not trust that they will continue to be so warm and fuzzy.
Imagine if VSCode becomes the defacto code editor. Then they add seamless integration with GitHub, including value-added features which are not available from other providers like gitlab. Developers accept it because everyone uses GitHub anyway. Then they add features to GitHub to integrate seamlessly with Azure, and bug tickets related to GitHub plugins for interop with AWS start to take longer and longer to be resolved. Then maybe one day they change the terms of service, and it's no longer allowed to develop GitHub plugins which compete with Azure. Then they release an update to VSCode which uses deep learning for code completion. On Windows it uses a new DX12-powered subsystem which makes it fast and responsive, while on Mac and Linux it falls back to a single-threaded solution which makes the whole application feel laggy.
In a scenario like that, it would be in principal possible to fork VSCode and make a more platorm-agnostic version, but how realistic is it that an individual, or even a small team will be able to keep up with a large corporation which seeks to make such an effort less successful.
Open source software is great, but if Microsoft owns the governance of those projects, and the up-streams and down-streams, they still have a lot of power over them.
This is what happened with Java, Go and Javascript growing rapidly while .NET took a long time to get out of legacy/desktop phase, partly because the tooling was fantastic but isolated to their own Windows platform. They've learned their lesson and have realized there are better businesses by providing the compute and making it easy to use with free and plentiful tools.
Fine if you just need PaaS app + RDB though.
You will need time to get used to it. I even use AWS for a Windows instance.
https://www.youtube.com/watch?v=Vhh_GeBPOhs
Granted, they weren't releasing much open source then, but it was all free to use, and the quality was far above open source alternatives (e.g. think the Visual Studio debugger vs. GDB wrappers).
I think they just naturally figured out that there's zero advantage to keeping developer tools closed source.
And yeah, Azure is a booming business for them. VSCode has a bunch of first-party extensions that reduce friction for working on their platform.
Trying to work with other databases after using SQL Studio is incredibly frustrating
https://en.wikipedia.org/wiki/Visual_J%2B%2B
Microsoft does the same thing over and over - "embrace" a technology, "extend" it by adding some extra stuff to it that happens to work best on Windows then "extinguish" the tech once people are locked in.
Also see: Internet Explorer or Kerberos or Office document interoperability or AIM (messenger) or half a dozen other things.