Firstly we can learn a lot, not merely from kamtza and bar kamtza but the zealots and sicari etc.
The situation prior to the churban was a disaster, there were heretics galore, the economic situation was terrible etc.
Was the rebbelion doomed from the beginning? I'm not sure? Certainly the rebbelion was doomed due to infighting in ways that are bederech hateva and gezayra milmala.
Were the rebel leaders evil or corrupted by power and brainwashed ideologies? The more I study of the period the more it's conflicting.
Like for example, the roman's were defiling the mikdash, I'm sure many felt that they were following in chashmonaims way.