"Double down" means to commit more effort or resources when stakes are...
https://wiki-neon.win/index.php/What_Is_a_Dead_Metaphor_in_Linguistics%3F_An_Insider%E2%80%99s_Guide_for_ESL_Learners_and_Word_Nerds
"Double down" means to commit more effort or resources when stakes are high—like in blackjack when you double your bet after the first two cards