Think about it. If you're trying to keep all your current players from transferring, why would you let a potentially disgruntled former coach talk to them?
I'm sure, as they were negotiating severance, there were terms laid out about who he can and can't talk to.
When you fire someone in an office, you typically escort them out of the building. This is the same thing...just on a more public scale.
Jim did not talk to the players after he was fired, and has not contacted them since being fired.