Re: When you have the $$$$$$$$$$$$$$
Microsoft's mistake was releasing a brand new mobile OS - Windows Phone 7 - and then almost immediately (within about 12 months of launch) announcing it was a dead end and there would be no upgrade path to the next version 8 (which also wouldn't be backward compatible with the old version). And then that next version was late, and by the time it appeared the mobile market for Microsoft was totally and irrevocably dead.
So basically, it was a botched Windows Phone launch and non-existent upgrade roadmap that doomed the platform, because they were far too late to the party so small things like rewarding customer loyalty or speccing sustainable rather than barely adequate hardware were considered unnecessary.
They could have been late and still had a chance, if only they hadn't abandoned their initial customer base. That was such a dick move.