The same reason the GOP didn't do anything about the border or gun rights when they had the chance. Why solve an issue when you can use it to get people to vote in the next election? Its a gamification of government. They are more concerned with keeping their jobs than governing.
Trump had the Wait in Mexico policy which was great. GOP never promised anything on gun rights, but Trump single-handedly banned bump stocks after the Las Vegas massacre which is more than Obama ever side on gun control.