After the previous killing phase, when the True Celestial announced the early end of the tower challenge, those remaining competitors grew fearful of fighting and dying when they were so close to prospering.
Even if they weren't the most likely to get the True Celestial's inheritance, they could return to their worlds and live in peace for a few centuries or even millennia, given the difficulty of reaching level 125.
Meanwhile, those who were almost certain to be among the finalists were the ones who most wanted to prolong their inheritance. They wouldn't fight or kill their opponents carelessly at this point. It made sense to push the challenge to the limit and get more opportunities to strengthen themselves.