Obama had loads of "political capital" in 2008 and the Republicans still voted against everything he proposed. "Political capital" isn't a thing that really exists anymore.
Damn right they did. Would you support something so diametrically opposite to your principles just because the president has "political capital"? Really, this question should be asked.
If a republican came in with a landslide and had the same majority Obama did and the first item on the agenda was to eliminate the EPA. Would you support that because you think its owed?