The tribune were and were not gods. They had the powers of one, only when fully recharged by the Heart of Lorkan. However, that power would wane over time and required them to recharge it by the heart again. However, when the heart was destroyed the survivors lost all traces of godhood.
Its sorta a borrowed godhood, never a true ascension into aetherius.
The Heart of Lorkan, was just that the heart of the Aedra Lorkan after it was ripped from his chest and thrown to Nirn, giving rise to the Red Mountain.
In the end, without that power the Tribunal was just as mortal as anyone.
Well, Nerevar, Vivic, Amalaxia (Nerevar's wife), Sotha Sil, and Dagoth Ur discovered the Heart of Lorkhan, which had been used by the Dwemer to be part of the Numidium (thier attempt at making a God). The Chimer (later became Dunmer) went to war with the Dwemer over the Numidium, and the war ended with the disappearnce of the Dwemer. This left Nerevar, Dagoth Ur, Amalaxia, Vivic, and Sotha Sil with the question of what to d with the Heart of Lorkhan. I forget the specifics about Dagoth Ur, but he ended up dead (supposedly), and Nerevar died shortly thereafter (possibly killed by Amalaxia). Vivic, Amalaxia, and Sotha Sil then studied how the Heart of Lorkhan was supposed to work, and after a few years went back and used it to become Gods. Dagoth Ur had also used the Heart of Lorkhan and had been kept alive, albiet without a body. The use of the Heart of Lorkhan angered Azura, and she cursed the Chimer causing their skin to turn black and their eyes to turn red (usually, this apparently was changed with Skyrim allowing you to choose different eye colors) and starting the prophecy of the Neravarine.
Over time the power that the Heart gave them would wane, mostly because it appears the the Heart was an inherently "evil" object, and it's powers were supposed to be used for evil which was something the Tribunal were not doing. Eventually, Vivic, Sotha Sil, and Amalaxia went to renew their power, but were met by Dagoth Ur who ended up driving them off. The Tribunal then created the Ghostfence to keep Dagoth Ur and his blighted creatures inside of Red Mountain, which didn't work (damn cliff racers!) as well as connections to other dwemer ruins outside of the Ghostfence. Sotha Sil and Amalaxia both gave up maintaining the Ghostfence, making Vivic handle of the work...
Uriel VII sends a prisoner to Vvardenfell, who becomes the Nerevarine, destroys the Heart of Lorkhan and leads to the downfall of all but Vivic. Vivic later dies later during the eruption of Red Mountain.
An abridged version of Morrowind and the Dunmer Tribunal.
Hold on, they actually re-wrote time? I thought Vivec just used his poetic skills to pretend all the dumb stuff he did was intentional for all the good things to happen (like persecuting the Nerevarine), and that he was only embellishing his past with clever words.
They didn't re-write time as much as they re-wrote history. They also were not true gods, as they could not reverse what Azura did to them, they were pretty much very powerful and immortal (for a time) mages.
The persecution of the Nerevarine was caused by Vivic becoming weak because he had to maintain the Ghostfence. This allowed the Ordinators to become even more fanatical and brutal in dealing with anyone who had started to lose faith in the Tribunal, worshiped the Nine Divines (until Morrowind became part of the Septim Empire), and those who believed in the Nerevarine.