If a right wing party can win in Germany, that’s a sign the left wing and centrist parties completely sucked and ignored voter concerns for too long. Let’s start there.
It comes down to ignoring voters will drive them to people who don’t ignore them.
It may be that in the US we now have a bit of an advantage at stopping the slide to the extreme right wing. The advantage being the total incompetence of the Trump administration which is now become obvious even to those outside of the left-leaning bubbles. His approval ratings are now right around 33% which is really quite abysmal for a president at this point in their 2nd term.