Through the power of pure bullshit. Welcome to the Thousand Year Blood War Arc.
Gremmy is a character that flat out does not belong in Bleach. His ability is too broken for the verse to handle.
Kubo has this habit of coming up with all sorts of fantastical abilities (some far better implemented than others) only to have them lose to brute meatheads whose only specialty is whacking things real hard.
No amount of brute strength should allow anyone to defeat a legit reality warper.