Let’s take today’s equivalent - what’s the likelihood of Amazon not offering AWS or even Microsoft walking away from Azure and pulling the rug out from under developers?

Even businesses that chose Microsoft technology in the 90s when they were the clear leader have had a relatively painless upgrade and support path. They abandoned VB6 15 years ago, but you can still wrap your VB6 code as a COM object and interact with C#.

I’m saying that it is the safer bet to go with the largest provider with the largest customer base. In the 80s that would be IBM, in the 90s, MS over SUN (and the royal claustrof%%% that Java has become under Oracle) or Borland.

What is the "largest customer base" relative to? In the early 2000s, most Fortune 100s used Solaris [1]- presumably this trend started in the 90s, so I don't know why you think that a manager during that time period would choose Microsoft over Sun except for specific use cases (e.g., smaller hosting providers).

Let's look at yesterday's equivalent to AWS- Sun Grid. Sun was viewed back during the first dotcom era in much the same way that AWS is today. All that it would take to completely bork it would be an economic catastrophe that mirrors the first dotcom bubble. Obviously, Sun Grid is no more.

[1] https://news.netcraft.com/archives/2004/11/16/solaris_remain...

Solaris didn’t disappear overnight like Smyte did. When Sun was acquired by Oracle they just didn’t abandon thier customers - that would have been too value destroying.

You can still buy Solaris based systems today but you would have plenty of time to migrate. But seeing the writing on the wall you would have plenty of time to migrate.