I remember them buying lots of companies, its what large companies do, especially large companies who have cash on hand. Years ago I had a company that had lots of cash on hand and our shareholders certainly didn't want that money sitting around in the bank making interest (interest isn't need enough to keep shareholders happy, as they can do that on their own), so we went out and bought some companies (companies that we could increase their market share through our marketing, companies that we could use to expand our client base, companies that expanded our product feature set, companies that prevent our competitors from expanding their product feature set, etc). Now Microsoft often buys companies just because they want the staff and not the product(s) as I mentioned before its the fastest way to acquire great employees.
I've been acquired a couple of times as well and each time it was a good deal as the company that acquired us had better marketing as we were tech startups so we had a great product and all the technical skills to create it, but we needed their marketing to get the product out there and be successful.
Sometimes when you start a company you have an exit strategy in place and often that involves being bought out by a bigger company like Microsoft. I like starting companies and creating products, but I don't and can't run them forever as that takes a different mindset then what I have (I'm good for designing and building the ship, loading it up and getting it out of port and running the narrows etc, but once she is underway on the open seas, better get a different captain as I'm likely to keep playing with it till the point that I end up trying to sail the ship capsized as I'm an agent of change).
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