They're definitely very threatened by open source - a lot of software infrastructure these days is built off of open source software. In the 2000s, it wasn't. It was Microsoft, MSS, COM, Windows server, etc all the way down. Microsoft has basically been earned alive by open source software, it's just hard to tell because they were so huge that, even taken down a few pegs, they're still big.
Even today, Azure and AWS are not really cheaper or better - for most situations, they're more expensive, and less flexible than what can be done with OS infrastructure. For companies who are successful making software, Azure is more of a kneecap and a regret. Many switch away from cloud, despite that process being deliberately painful - a shocking mirror of how it was switching away from Microsoft infrastructure of the past.
Even today, Azure and AWS are not really cheaper or better - for most situations, they're more expensive, and less flexible than what can be done with OS infrastructure. For companies who are successful making software, Azure is more of a kneecap and a regret. Many switch away from cloud, despite that process being deliberately painful - a shocking mirror of how it was switching away from Microsoft infrastructure of the past.