The Orion Nebula

What influences how likely a rebellion is to occur on a planet? Is a Unification government's citizens more likely to rise up if they are captured? Likewise is a dictatorship more likely to have captured populations rise up than a Democracy?

What influences how many rebels fight in the rebellion?

Does ground combat influence rebellion effectiveness?

I tried searching around but I couldn't find any information on it; any information would be helpful, thanks.

From my experience, the number of marines you leave behind on a planet after you capture it, appears to make a difference as related to the entire pop remaining.
So, if you conquer a 30 pop Sakkra planet, with 30 pop remaining, and leave 4 marines from 1 transport behind, they will likely rebell.
Compared to the same planet, with its pop bombed down to 2 pop, and that same 4 marines to control the pop.
So, the higher the pop left on the planet you capture, try to exceed this number in marines you leave behind.
And Obviously, buy your Alien Control Center as soon as you can.