He's still not as adept at hacking human brains; it takes so long in comparison to machines. And... he's more used to being partnered up with 2B, who would cover him while he hacks the machines with more complicated attack barriers. The thought of 2B is enough to distact him just long enough for his reaction to the the ground tremour to be delayed, getting caught wrong-footed.

Stumbling, he finds himself getting kicked out of Strange's head once more. Damn it! As he quickly regains his footing, 9S folds his arms and explains in a peevish tone, "You can't focus on breaking the spell when you're busy casting something else, can you? If I can't directly stop someone from attacking us, I can probably redirect their efforts."