Toi, your logic about rabanut hechsher could be equally applied to charedi yeshivos – i.e. since three charedi yeshivos in Yerushalayim were investigated and found to be defrauding the government with fake id’s of nonexistent kollel learners, therefore all yeshivos are “of questionable status”.
You and I and most people would call such an assertion absurd, but you seem to be OK with the same assertion being made about the Rabanut.