Approval ratings are unscientific, fleeting, and wildly variable, even among Presidents that go on to be reelected. It is a stat you take with a grain of salt, especially 6 months into a presidency. Even the polls for the actual election, which get far more money to spend, were wildly inaccurate especially in recent elections.
If Trump's moves pan out in the positive for American people over the next year or two, controversial as they may be in the present, then sentiment will increase, plain and simple.
JD Vance is quite popular among Republicans and reasonably popular among independents, which is all you need to win the presidency. The Democrats, on the other hand, have no heir apparent and have quite a few structural issues within their own party at the national level. We'll see what the actual field looks like in 2028 but that is a long ways off and a lot will change between now and then.
