None of what you said explains how Microsoft today (not 15 years ago, or in some hypothetical future) will have a monopoly before or after this acquisition.

By allowing MS to do this the courts are signing to the world that smaller companies shouldn’t even bother competing because they can never outspend MS’s war chest.

Which company would you have expected to compete in the console space in the foreseeable future that will have changed their minds because of this acquisition? I’m not aware of any, but I wouldn’t mind being shown that this is a real concern.