In the current environment, what do you propose they do?
They control the House of Representatives, so they could strip the NSA of funding.
Also, they could actually investigate and push for prosecution of the wrongdoers [essentially the whole agency, plus contractors] — would that be a mess
or open a can of worms
? Quite possibly. However, it would also show that the Republican party isn't just all talk, and that it's willing to get into uncomfortable places to get rid of corruption — but they didn't, which shows that they accept the NSA's lawlessness, and approve of it.
Seriously, if they made a honest, vigorous push against it even if they were stymied by the Democrats (though I think the topic is so toxic even the Democrats wouldn't be able to stand against an honest opposition) they would garner support from the general population. It was seriously a no lose proposition for them (or even the Democrats, had they capitalized on the opportunity) — the non-action and de facto defense of the NSA shows [to me] exactly that these elites are unified in their statist ideology.