... that the Moon was part of Mars?

... that the Moon was part of Mars?

... and you can keep your Doctor...
President Trump hasn't been to all 57 states yet!
Of all the possible sources to try to interpret what President Trump was trying to say, . . . it looks like VOX got it right:
"But Trump was likely referring to NASA’s plan to build up resources on and around the Moon in a sustainable way. In other words, the idea that whatever we build for a moon mission should also serve future missions to Mars, or beyond in our solar system. This has been the plan all along: establish a more permanent human outpost around the moon so we can better prepare for a much longer and harder journey to Mars or beyond."
And the VOX explanation included more details:
"With its 2017 directive from the Trump administration, NASA got to work, drafting plans to achieve a long-term human presence on the moon.
The centerpiece of the plan was a space station called the Gateway, or lunar Gateway. It’s a space station, but instead of orbiting Earth, it will orbit the moon and serve as a launching ground for missions to the lunar surface. It would be reusable and nimble: NASA could change its orbit to pass over any location on the moon.
And like the ISS, the Gateway could be — potentially — continuously occupied by astronauts, establishing a permanent human presence near the moon. And like the ISS, the Gateway could be — potentially — continuously occupied by astronauts, establishing a permanent human presence near the moon. The benefit of the Gateway is that it’s multipurpose. It could serve as a stepping stone to a permanent base on the surface of the moon, and it would be a decent launching point for missions to Mars or to asteroids."
[boldface added-DonDiego]