The pilot seat moving full aft would be a horrible situation to contend with during rotation off a limiting runway.
If that is indeed what happened.
From my experience, the B737 seat rail mechanism is very robust. Even if the seat rail pin is not properly locked into the hole prior to takeoff, it will slide back and lock into the next hole with any aft movement (such as would be experienced during rotation).
Regardless, any pilot with any sense of self preservation would of course rock their seat fore/aft after adjustment to ensure it is locked in place.
I am lucky to work for an airline with an immaculate maintenance culture. However, I have once experienced a seat that did not lock in very well after adjustment. I of course ensured it was fixed prior to departure. I can’t remember exactly what was done, but it was probably just a lubrication.
If this is indeed what happened, the causal factor could turn out to be poor maintenance.
As for the pilots not being aware of the impact or damage, there are several examples of tail stikes (including localiser anntena strikes) by well-regarded airlines that the pilots were completely unaware of. The tail is a long way from a noisy cockpit, even in a B737.
I was a brick-layer’s labourer at some point before I was a pilot. Apart from learning how to swear properly, I also learned that a thin brick wall is very weak unless it is supported by another perpendicular brick wall or another strong structure. The wall in the video shows neither. You could probably push that wall down with the appendage between your legs if you saw anyone attractive enough. The 737 undercarriage sure as hell wouldn’t be bothered by that “so called wall”.
Sheesh, the tyres were still inflated after the impact with the brick wall. Brick Smish.