I'm pretty sure it started with Lil B "Thank You Based God".
Lil B was an underground rapper with... varying levels of quality (at least at the time). His thing was calling himself "Based God" as people were calling him "based" as a negative (presumably to mean he was dumb), but thanks to his music and understanding internet culture and turning it in his favour, he managed to turn "based" from something that was negative to a positive.
Then 4chan got ahold of it for Donald Trump's election and that word has never recovered.