Since any idiot would know that destroying public records is a crime, I can imagine only that the crimes they were covering up were worse than the crime of destroying public records.
I used to live near Lynn, Massachusetts (”Lynn, Lynn, City of Sin”). There and in Mass. government generally, no amount of criminality is ever petty enough to remain an untapped resource for enterprising politicians. Usually, outgoing officeholders don’t worry about their replacement, who is likely a Democrat and beholden to the same interests. When the rare GOP member wins something, it might be time for a Shredding and Burning Party.