The teachings of the Jiejiao Sect were to seize a lifeline for the living beings of Heaven and Earth.
Therefore, Leader Tongtian, having no other choice, chose to actively face the tribulation. He wanted to use the Enshrinement Calamity to prove his Tao and to seize a lifeline for the Jiejiao Sect.
If successful, Leader Tongtian would have proven his own way and gained tremendous benefits, thereby advancing further to a higher realm.
If he failed, the Jiejiao Sect would cease to exist!
It was later proven that Leader Tongtian was successful in the end. Although the Jiejiao Sect was destroyed, Saintess Wudang survived, preserving the last lifeline for the Jiejiao Sect.
Leader Tongtian also, due to the destruction of the Jiejiao Sect, managed to break and then establish himself, making significant advances in his realm.