Obviously Bush is doing this for political reasons. I hardly make up my mind on things based on what Bush thinks. Bush's mind follows the money usually and he's a phenomenal political fund raiser regardless of what people think of his lack of intelligence.
There is no apparent economic gain to be made with a space program like his. If the Moon and Mars new made of solid gold, it still wouldn't be profitable to mine either planetary body. It simply costs too much to get to either place.
I look at it like this. Normally we throw away billions on military toys that don't really work. We do it to cover government waste and corruption and we do it to help our economy. We have to justify it occasionally by going to war or conflicts. In such skirmishes, people will die, usually hundreds at least.
The space program is a hole that is much nicer to throw money into though. To justify it we just launch a few people off planet to possibly die and it makes us feel like we're advancing as a species. We remember our sci fi entertainment and hope we are going in that direction.
Regardless of what we think of Bush, this is progress. It's a better hole and will possibly someday be a step to advance the human race. It give optimism despite the facts and that in itself is enough to boost the economy.