Some of those guys in the beginning doing squats have TERRIBLE form.
Their form looks bad to you. You'll lose form when you're lifting near to max effort.
Knees turned far outwards, feet spread way too far (and most likely everted)
There are a couple different styles to squatting. Every lifter has different hip/back mobility. They have to choose one that'll help them get low enough to get the green light in a competition meet.
using a bench to sit down on.
It's called Boxed squat. Helps your body get used to being under heavy weight & strengthening the assisting muscles for squats.
All recipe for disaster on the squat. Can hardly believe they've gotten that far without some kind of serious injury.
To an untrained person yes it looks very dangerous. Look at Olympic lifters, they lift heavy weights gracefully over their heads. It takes years of practice to get your form down correct. Even with basic lifts like bench,dead,squats.