Nor do single issues get mandates even when a president does have an overwhelming victory. Voters do not select specific issues to vote on, they vote for a person based on their overall platform.
Trump also talked about how he was going to focus on deporting violent criminals. And now that that is no longer the case, the goalpost is being moved to... any crimes. And now again to anyone that has outstanding charges, but no conviction. And now it's hey, they're here illegally, so that's a crime, right! We'll have to ignore the fact that a good chunk of those being deported also entered using a legal process that puts them in limbo - ICE has been grabbing people showing up at their immigration court cases.