I think it's safe to say that SoftBank was the trigger, by buying up the meme stocks that are relatively safe bets (Tesla, Amazon, etc), which WSB/Robinhood traders had their eyes on. The Tesla/Amazon traders amplified the signal, and their gains posted everywhere on Twitter, Insta, Reddit, etc. encouraged people to plow more money into the markets, especially in the direction of the meme stocks. Then as S&P started gaining, people noticed and just continued plowing money into the index. Which is why outside of Nasdaq, tech and S&P, there are hardly any movements in the market.
Buying options is still visibility, encouraging would-be traders to register on Robinhood and buy some amount of stock. For instance, my old college mate, a current PhD candidate, joined Robinhood and started trading around March. And of course, when he asked me for recommendations, I told him to play safe and go with the S&P stocks and resilient tech stocks. Then of course, he went full on WSB mode, and now he's "eating tendies while his wife is hanging out with her boyfriend".