For the sake of argument, not specifically weighing in on the truth of whatever the PSL is going though...
If the feds successfully smear one leader with a scandal, they win a minor victory. If the leadership circle closes ranks and moves to protect the smeared leader, the feds win a big victory by bringing all of them into question.
Anyone who is willing to take a bullet should also be willing to take a fall regardless of the truth. Any cadre based party should have a pool of replacement leaders ready to step up.