Would it not be cheaper for Google, AWS, Alibaba
to get together and produce free/FLOSS replacements to the MS software that their customers use in the cloud ?
They do not need to start from scratch, there is plenty that would need a few extra features and interfaces to allow the enterprises' applications to work.
Obviously it will be more work than I suggest but it does not need to be 100% compatible - just as long as the effort to port workloads is not too hard.
Releasing this as Open Source will be vital so that enterprises can test it in-house ... some may use it in-house as well.
Note: they do not need to replace everything that MS produces, just what most of the cloud customers need. Start with the easy low hanging fruit.
Yes: it will cost but being able to take customers from MS should result in an overall gain.