Leverage 3 x SPX daily

I used 3LUS which is the 3x daily return, however while SPX has met its ATH this ETF is still about £19 away from it.
What gives, I have noticed that the daily rate is not 3x, however the downside isn’t 3x loss either! This ETF has 20% left to go before it meets it ATH which would mean SPX would have to have so massive daily rocket ships upride. Can anyone shed any light.
Does anyone know how the fund managers create 3x daily gain or loss? I assume they use options, are they 0DTE?

Because any 2X or 3X ETF has higher fees that eats into the performance, that’s why in net value you won’t see 3 times the annual yield, and that means ATH in Spx doesn’t mean ATH on 3X SP500.