"Double down" comes from blackjack, where you double your bet after seeing your...

https://qqpipi.com//index.php/Idioms_That_Sound_Negative_but_Are_Actually_Neutral

"Double down" comes from blackjack, where you double your bet after seeing your first two cards, aiming for a big win. Learners often misuse it to mean 'do something twice'—not quite. It’s about commitment, not repetition