Republicans stopped doing the Democrats’ dirty work for them. Democrats have always relied on corporate welfare. They created Ex-Im, they expanded Ex-Im. They liked that Ex-Im allowed them to steer money towards the technologies they liked (see the Obama Ex-Im’s effort to boost a flagging Solyndra). Chuck Schumer in 2015 made it clear he would use Ex-Im to raise money for Democrats.
Fostering government dependence is a good thing if you’re a Democrat, and that’s what corporate welfare does: It turns big business into the clientele of the welfare state.
But as long as Republicans were willing to take the lead on “pro-business” policies, Democrats were happy to play a mere supporting role. This always gave Barney Frank and Obama great ammunition with which to attack Republicans as hypocrites — opposing welfare for the poor, but favoring it for corporate America.
An anti-cronyism movement slowly grew on the Right, though.