It was a silly idea from some silly people who had a few well received time travel episodes and tried to capture lightning in a bottle by giving us a show with a big time travel McGuffin
It really wasn't a bad idea and as Brannon pointed out years ago it really would be better served as its own series or mini-series. Afterall, to do justice to it you have to take the time to introduce all the players and agendas and to do that it would basically start displacing ENT as a prequel as you dedicate all the energy into setting it up and advancing it. And as we saw many times the TCW agents like Daniels should really be the protagonists. But if that is the case Archer et al become peripheral and so B&B on a few occasions had to stretch the plausibility of temporal agents like Daniels sending inexperienced time travelers like Archer or T'Pol back in time to save the day("Carpenter Street").
Plus when you are doing a prequel, the audience wants to see how history unfolded on its own and not see an altered past heavily influenced by future forces mucking about.
A TCW is an ambitious and epic idea that it needs to be its own series like Lost where you can take the time to build up the mystery. Limiting it to one or two episodes won't do it justice. It is the kind of premise that needed Daniels and the time agents to be the stars. We could have visited different centuries, unknown events, familiar events depicted in other Trek series that were in jeopardy by undercover agents etc.
IThere seem to be 3 different agendas going on with the TCW: FG's meddling with the Kabal fraction of the Suliban, The Sphere Builders attempt make our part of the Galaxy one big expanse and Vosk's race who accidentally got trapped on Earth during WW2. Only 2 of which were properly resolved.
Well I think there was far more than three factions at work. There was the Tholians and possibly the Tandarans. And the Sphere Builders weren't a part of the TCW. They were just third parties who happen to possess time travel abilities.
