growing wheat in space to feed a starving planet

Ridiculous: I never said that. It would be possible to grow enough on the moon to support a colony there, but importing food to Earth is crazy expensive.

mining asteroids
Some people with a lot of money are actually spending some of that money on this.
BBC link

And you know we could rebuild Puerto Rico perfectly well, if they didn't all speak Spanish. It just takes money and maybe the Army Corps of Engineers for a while, but they don't get to vote so Trump would rather spend the money in Florida.