It's called consensus building. In the US, bills are often riddled with bits and pieces of pork barrel legislation that have nothing to do with the intent of the bill. In this case, FWD.us is trying to butter up these senators and representatives by advertising for something they want in hopes that the congressmen will return the favor when it comes time to vote for immigration "reform."
This is actually an example of providing political cover.
Immigration reform is not popular with conservatives, therefore politicians with conservative electorates (like Rubio, Graham, and Begich) might lose their next election if they vote for it. This makes them less likely to vote for it.
Running ads in conservative areas to promote immigration reform will not help; the dislike is too deeply held. FWD.us does not have nearly enough money or time to change such ingrained cultural beliefs.
So instead they run ads supporting the politicians on issues that conservatives already like--like energy development--to try to strengthen the conservative credentials of these politicians. That way the politicians will hopefully feel more secure in their seats, and therefore more comfortable with taking a risk by voting for immigration reform.
The hard part of this strategy is that you might have to run ads supporting things you personally disagree with, simply because it's a good political tactic. Musk probably decided that he cares about getting off oil more than he cares about passing immigration reform, so the balance was backward for him.
