Tomice pretended to be the D BEFORE Radekas' appearance (which means before Radekas said that I'll be investigated). It means that Tomice acted as a D with a plan. Even more, he sent a PM to Radekas, informing him about everything.
I don't get it how you don't understand that this was suicidal. If I was in Tomice's team, I'd have told him to act as whatever he wants, but not the D. The Gs knew who was the D and they needed to whack him. In order to whack him they needed him to stay calm and hidden, not to show himself and get the BGs protection.
It was incredibly stupid what Tomice did, and they were incredibly lucky that X was in jail.