I have no idea what the solution is. It’s not that the Americans haven’t tried. Oh yes, they have. Their system of checks and balances is one of the most intricate in the world, it just was not enough.
We saw a similar thing with the rise of Victor Orbán in Hungary. The social-democratic party was affected by a scandal, the left in general was deeply divided, and then the unimaginable happened: Orbán won elections with a two-thirds majority.
Two thirds, that is a deliberately high limit for changing the constitution. For a long time, it was deemed the gold standard for protecting democracies from gliding into tyranny. Unless the dam broke in Hungary.