... one which they also made a nice little profit of. $150M in the non-voting stock they bought in 1997 turned into $550M in 2003 when they sold most of it.
On the face of it that sounds like a burn on Microsoft, wisely found by studying the finances, but... by the nature of Apple being the best performing stock in the world for multiple years isn't the same true for most companies, that they could've made more money investing in Apple than in themselves?
Heck, maybe investing hundreds of millions in Apple today would, in X years, be worth more money than spending marketing money / development budgets for new features for their own products; or worth more than investing in OpenAI and related products - but it's not exactly something anyone would suggest Microsoft should do (in terms of just becoming a shareholder, of course there could be collaborations without changing this point).
Technically yes, but not really. It’s specifically valid to observe with regards to Microsoft because Microsoft did in actual fact hold hundreds of millions of dollars worth of Apple stock for a decent stretch of time. Most companies did not.
Microsoft chose to sell their Apple stock in 2003. This was entirely their choice. They didn't have to. They could have sold it in 2005 and made an additional billion dollars. They could have sold it in 2007 and made another ten billion dollars. They could have sold it today and made a hundred billion dollars.