Anti-trust law is not simple. In the case of MSFT and IE they were accused under the protects of the Sherman Anti-Trust Act[1] of using their monopoly position (Windows) to reduce consumer choice (bundling IE without letting users pick a different option). In the case of Apple and Google, it's more likely to fall under the Clayton Antitrust Act[2] as it's a matter of corporations collaborating to reduce consumer choice (but I am not a lawyer, and not even American, so I could be waaaay off the mark here.)

[1] https://www.investopedia.com/terms/s/sherman-antiturst-act.a...

[2] https://www.investopedia.com/terms/c/clayton-antitrust-act.a...