Not to mention launching to Mars from the moon is easier (in some respects, not all).
A Moon base will be a far harsher place than a Mars base. Mars is bizarrely similar to Earth - nearly the same length of day/night, similar axial tilt so similar seasonal patterns, nearly the exact same land area, and even calm weather. Notably the 'raging dust storm' in "The Martian" that was used to set up the crisis for the movie was one of the few things that was intentionally faked. The low atmospheric pressure on Mars means even the most brutal dust storm would feel like a slight breeze at most. It's also telling when you need to fake something to create a crisis, in an otherwise very hard sci-fi book!
2) Partial gravity
To be fair, the vacuum on the moon is also not comparable to the windy atmosphere on Mars.
The second is because the ISS is quite tiny. It has a total compressed volume of ~900m^3 contrasted against the 1000m^3 on Starship. Factor in its design of interconnected pods and the usable volume sharply decreases.
I do see Trumps side, that if they take decades to get anything done, maybe the project should be scrapped. But space-x has proven they can launch rockets reliably and cheaply, I believe we should use their innovation but to the moon before the red planet.