It’s selection bias, usually using a post hoc ergo propter hoc fallacy to rationalise it. “I prayed to a deity for the snake not to bite me, then the snake didn’t bite me, ipso facto goddidit.”
As you say, when the snake has a bad morning, and shows it’s displeasure, suddenly god is mysterious. You can’t dent a rationale like that. Plenty of people handle snakes without the pretence of a watching deity, and come to no harm, but then they have usually studied the reptiles for years, and have a deep respect for what they can do.