I’m not going to lie or cherry coat this for you. That deadlift is really rough. Was that a max or a heavy single? It really looks like you need to work on all the steps to me.
Take your time setting up. At least for now. That quick grip and rip is for people who have already built good form and can DL in their sleep. And even then, a lot of big pullers don’t do it that way.
The different methods of creating a stretch reflex in the hams are a more advanced move and unnecessary for basic form. Konstantin Konstantinov has a 939 raw beltless pull to his credit pulling this way.
Having mentioned him, keep in mind that it’s just his upper back that’s rounding, not so much his middle back. Your entire back is rounded. It’s what I call a fishing rod deadlift.
Here’s what I would do. Especially if you even do this with lighter easier sets. I would just re-learn how to deadlift. Start with half that weight and just try to nail perfect form 2x a week. Keep taking videos to evaluate your form Once your form is proficient with that weight bump it up 10lb next session. Don’t push the reps or sets, just focus on clean crisp reps. Doesn’t have to be like speed work, but you don’t want to be grinding any reps. Not just yet anyway.
Maybe even drop deadlifts altogether for a couple or a few weeks and pick an exercise that’s more a pure hip hinge. Romanian deadlifts are a great candidate for this.
You’re not hip hinging much at all. There’s just a little bit of knee extension and a lot of back extension.
It’s hard to tell from the angle (straight from the side is best), but I think your shoulders are way too far over the bar. Work on pushing your hips back and pulling your shoulder down (or pulling your lats into your back pocket whatever works best for you).
I used to have the same problem, but I’ve ironed it out using that same advice from these forums. I’ve just consolidated it for you.