They bought Android at a time when it had 0% market share. They changed direction significantly after the acquisition and grew from 0% to 80% over half a decade and then maintained that position. It was not a foregone conclusion that Android would be dominant after it was acquired. Also, it takes effort and skill to maintain your position in a competitive market, which they've managed for half a decade more.

People seriously underestimate how difficult it is to succeed and continue to succeed.