Someone yanked your chain with this one. Nobody gets a house or a job at Microsoft for buying Microsoft, these cases can't even register in the statistic of the total volume of orders. Every tech company would buy you a house if that worked, when a house is always a rounding error on the value of the contracts we're talking about.

They buy it because it's the "safe", "does everything" choice that "everyone else has". It's easier to deal with a single party than it is to get licenses and support from 20 other suppliers that then blame each other when there are issues at the border between 2 of the products. You can talk to anyone else who has Teams, your files are always fully compatible, all of the rest of your software integrates, single identity, etc. A lot of good it is that you have Google Meet and Libre Office when the partners you work closes to have Teams and MS Office.

Users are proficient with the products, you can find skilled admins everywhere. Incumbency has a lot of inertia.

So you have to pay millions in support contracts every year, it's the cost of doing business. So MS gets hacked every other day, what could you have done about it better when even MS (!!!) couldn't?