That's a flawed argument. Why wouldn't you want to hedge a risky bet, and one that's even quite highly correlated to Microsoft's own industry sector?
my impression is that many of these "investments" are structured IOUs for circular deals based on compute resources in exchange for LLM usage
Maybe that will be true someday. But, right now, they are burning billions of dollars every quarter. Their expenses far far outweigh their income and they are nowhere near profitability.