Lots of companies reached monopoly status because they were simply better than the competition.
The point of breaking up monopolies is not to make a moral statement about the company, but because we've found that monopolies are generally bad for society.
Is it really though? Bing has been consistently worse than Google over the years. Maybe our definition of vendor lock-in needs to change.
Honestly at this point it doesn't even matter how good Bing is - we've been unconsciously trained to work with Google's algorithm in particular and they just have a de facto monopoly on the mental process a person goes through to formulate a search. Everyone's workflow everywhere will be worse and take more time if they voluntarily stop using Google, that's not what I consider a fair competitive landscape.