So Zhang Yi might be able to buy some time for sects that would actually go into isolation if the beasts decided to attack them after that Zhang Yi would not feel guilty even if all the sects were eliminated.
The 15 beasts were attacking the Zhang Yi clones and even with some clones receiving attacks from 2 beasts from the Eternal Realm they were still able to defend themselves, this gave the divine plane's Eternal Realm elders more time to rest and recover a little from the fight.
These elders were not just thinking about them and listening to why Zhang Yi had come to help and the situation of the divine plane they decided to retreat little by little while defending themselves from the attacks of the beasts.
So when the great sects were ready to retreat they would have time to flee, the beasts continued to attack because they knew that this was how they were hurting the real body of Zhang Yi who was among the clones.
