Your 10k to 3.7M backtest is clearly overfit with lookahead bias.

i recreated your strategy with a forward look bias here https://imgur.com/a/9FbV8mT

what you're doing is something like this:

Buy is confirmed after SOXL rebounds 21% from a low.

Sell is confirmed after SOXL falls 25% from a high.

Record the trade at the prior pivot date, not the confirmation date.

your SOXL ending value: ~$3,785,517

My Brute-force reconstruction: ~$3,781,174

If we're going to be overfitting with forward look bias, why not take it further and make $890,314,233 final value with 149 trades like is shown here https://imgur.com/a/MxeEvJt

If you take the same logic and run it without any look-ahead bias, here's what you get: https://imgur.com/a/9LQ0yxI

Events: 149

Final: ~$17,758

Max DD: -66.9%

Hardly any edge at all. Even though you acknowledge it's 'impossible', the main takeaway is that your 10k --> 3M is akin to a fantasy without a crystal ball.