The tail of the plane hit the runway five times before the captain ordered full thrust at the last minute
The crew must be new to the craft to not have seat of the pants feel for roll out and transition.
Tail Strikes in the A340 are a real problem, and this is far from the first. In fact, they are strengthened for tail strikes.
Exactly. The thrust is reduced on most takeoffs. Still, an average crew can sense when the takeoff is not accelerating normally. Airline operations attempt to maximize engine life by using reduced power settings ie matching the thrust to that necessary to lift the airplane safely given runway length, temperature, altitude, and possible obstacles. That greatly prolongs engine life and the manufacturer warranty.
Some conditions preclude reduced takeoffs—contaminated runway, tailwind, or missing panels on the airplane (increased drag) etc.
This is an overview—hope you can get a better picture.