In the specific case of the Thrintum or Slavers, their mind control abilities would make it rather probable to take over the Tnuctipun - and even so in the end some of the Tnuctipun managed to revolt and eventually all intelligent life in the galaxy was destroyed in the revolt.
..This being the short version. The struggle nevertheless emerges as a true epic, spanning countless generations and involving sacrifices and patient subtlety that puts any "resistance" stories of our world to shame.
In the specific case of the Kzin, a group of Kzin was recruited as mercenaries by the Joktai and no doubt learned a lot about Joktai science and technology before overthrowing the Joktai. This could have proceeded like a number of take overs by "barbarian" mercenary soldiers in Earth history, such as in the fall of the western Roman Empire and especially the legends of the Anglo-Saxon conquest in Britain, which it may be remembered took over eight hundred years to complete.
I believe the correct spelling is "Jotoki". And the extended explanation for Kzinti technology, as per Dean Ing's short stories that Niven embraced, is that not only did the Kzinti (who already were flying jet planes) get tech from turning tables on their Jotoki masters back when they were clever - they also deliberately dumbed themselves down when they obtained the technological means, turning the females into mindless gangster molls and sex toys, and the males into almost equally brainless caricatures of brawny superstuds. Guile was something they lost in the process, a price they considered a bargain for the ability to live their most cherished fantasy.
In my Klingon theory, I imagine that the first Klingons were educated by their creators, and may have served them for lifetimes before revolting and overthrowing them. The myth that the first two Klingons killed their creator gods would be just a myth based on a very dim and distorted memory of the actual event.
That it's but a myth now suggests great timespans and allows for a lot of interesting stuff after the fact, though. The current social structure (and biology, as the Klingons are also described as avid self-experimenters!) might be more the result of these later events than the original revolt, then.
So I imagine that the Klingon revolt against their creators would been much more likely to succeed that the English villagers efforts in The High Crusade.
Of course, the Klingons may have gotten enslaved at a late timepoint, too, being already Kzin-advanced rather than English-primitive. The event just gets pushed back to pre-Kahlessian times out of shame. Klingons
are supposed to be good at rewriting their history, after all, as made explicit by Gowron's efforts and implicit in their great bragging tradition... The enslavers then could be the Hur'q, who onscreen are merely considered raiders rather than occupiers, but who get the Klingon throne for a brief time in the novels.
But I don't think the old English would have been any more stupid than the folks of today. Give them a few decent meals, and they'd be up to speed on the nature of their gods or oppressors, even if they hadn't been taught at school exactly what "coming from the fourth planet of Zeta Ridiculi" means. Conversely, clever as we may consider ourselves, we'd be out of our depth with any true interstellar travelers; if generic human ingenuity and aggression didn't suffice for the English, it wouldn't suffice for our revolt, either.
Timo Saloniemi