Microsoft is a company run by people, and those people have changed (the "they" you mentioned). Gates & Balmer are now nothing more than shareholders (Gates stepped down from the board in March this year). Believe it or not, it's people that determine how a company is run and the people running Microsoft today are not the people that were running it in the 80s & 90s.
Large business units with billions in revenue take years to change direction, and we've seen that clearly happen under Nadella.