Chris has always tried to maintain his dominance over the other cats in the house. That is probably why he fights with Frankie sometimes because Frankie does not accept him as the boss. Puck did, but Chris still needed to prove he was the boss by holding Puck down by the neck. Sometimes, he would even straddle Puck and drag him across the floor by the back of the neck.
After Puck died, he started doing the same thing to Floki. I notice it perhaps once or twice a month. Often he does it while standing but not always. Here is the latest example.
I could be wrong about the reason for this. If anyone knows what this behavior means, please let me know.