The Tea Party and MAGA are not related. Stop getting your political analysis from Brits who can't point to Idaho on a map.MAGA has been 20 years in the making - there was a groundswell that made pandering to the tea party important.
It's not going away just because the current cult leader dies / leaves office (these to things will most likely be simultaneous). I certainly don't see the Supreme Court returning to normal just because Trump goes awy.
Murca F*** Yeah! goes back even further
They may not represent the majority of Americans (and note, my issue is the country, not the individuals) but they represent a strong enough faction to win elections.