Just checked and one of the signings is Eden Hazard. That Chelsea team isn't winning shit without him. It's not about a points deduction. That benefits us and this isn't about that, but whatever they won during that period should be struck from record. If you're cheating to win the league, you haven't won the league. Simple.
It doesn't matter if they declared (some of) it, either. If I decapitate a nun and walk into Steelhouse (RIP) with the severed head saying "my bad, boss", am I walking free? It's cheating. Apparently this is very important these days, so penalise them.