Some thoughts...

Perhaps they've decided to accept that several states and many millions of Americans have decided to buy into the ACA, and continuing to oppose it just puts them more solidly on the unpopular side.

Or perhaps they've realized that instead of trying again and again and again to kill it, and failing again and again and again, they could have put all that energy into something that might have actually benefited the country.

Perhaps they're just tired of having their noses rubbed in their own crap.

Or they're simply moving on to the next phase of lunacy that will alienate them even further from mainstream America.