Turns out Vivec used the time to take his revenge on Azura for taking Godhood away:
When Hogithum arrived, the priest Ainoryl was given the task of summoning Azura within the Hall. After the preparations were made, Azura was summoned but before the judges could ask her any questions Vivec interrupts revealing his true intentions for the assembly of the trial. Vivec used his shadow to wrap around Azura and reveal her neonymic, fully manifesting and binding her to http://elderscrolls.wikia.com/wiki/Mundus. Vivec then proceeded to call forth her protonymic, further binding her to the realm and releasing the mortal soul of Almalexia which was trapped within Azura's Star. With Azura fully bound to Mundus, Vivec revealed to her his ability to utilize http://elderscrolls.wikia.com/wiki/CHIM and then assembled his spear http://elderscrolls.wikia.com/wiki/Muatra from the bones of his armor, thrusting it down her throat and banishing her from the world. With Azura defeated, Vivec thanked his court for unintentionally helping him get his long awaited revenge on Azura, and in conclusion, placed Alandro Sul's ringlet in his mouth which issued a voice stating the secret message found in the http://elderscrolls.wikia.com/wiki/36_Lessons_of_Vivec, "He was not born a god. His destiny did not lead him to this crime. He chose this path of his own free will. He stole the godhood and murdered the Hortator." Vivec then vanishes, implying that his disappearance was done so on his own initiative
And he also didnt use his last power to put down the meteor that hanged over Vivec city, instead leaving it deliberately in place, knowing that when he looses power, it will fall down (Meaning he wanted Dunmer to die once he looses his powers)