Why would he still work for Microsoft if he was fired?

He probably is jokingly referring to the Nokia acquisition, which at that time is ran by an ex-Microsoft executive, whom rejoins Microsoft after the acquisition.

https://www.google.com/amp/s/www.nytimes.com/2013/09/04/tech...

Sorry but small correction:

s/ran by/ran into the ground by/g

Oh yes, I forgot about that important detail. MS was able to buy at a greatly discounted price due to that.