To make you analogy more accurate, this single employer would be paying the employees not to work for anyone else. And in that case, yes, the employees would be the ones that have the power since they are getting money for nothing.
It's not for nothing though - the employer is buying their productive capacity. The fact that the employer chooses to do nothing with it is entirely irrelevant.
Same issue with Google - by using their market power to monopolize search power across devices and OSes, they are effectively locking out any other potential entrants. That this is being done to enhance a completely different line of business (ads) is classic anti-competitive behavior.
What you are describing is a monopsony, they are illegal, and the employer is considered to have the most power in that relation because the employees are atomized.
