>I'm a rocket scientist

That dont impress me much.

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>And yet... I don't see the point in the Mars missions

What Mars missions? Which rockets do you work on again? The only Mars missions are things like the NASA rovers etc.

>I suspect that the real reason is Elon Musk trying to force America to pay for something they don't need

Which rocket do you scientist for again? SpaceX won the HLS program, most did not give them a chance. So its the other way round, they are providing services that the US needs.