He let it cook too long on each side. He wasn’t confident in cooking it and he doesn’t seemed to have watched any tutorials to equip him with the knowledge of what to do.That’s why he cut into it to check if it was done. Which is a cardinal sin.
By cutting into it, he exposes the interior of the steak to the heat of the pan. The juices will drip into the skillet causing it to sizzle, creating steam and therefore more heat.
I know he was pressing the life out of that steak; pressing all the juice out of the meat till the juices dry out of the pan. Another cardinal sin.
That steak is thicker, so he probably could have cooked it for 3/4 mins on each side and let it rest and residual heat would have cooked it the rest of the way for a medium done-ness. It looks like he cooked it for 7 mins on each side.
I think he cooked it for longer than he should have because he wanted to make sure it wasn’t raw. He clearly doesn’t cook much.
If you want a good steak, do the opposite of what he did. A lot of ppl say they don’t like steak because they’ve had it like this.