I went through something like this at the company I worked for. A VP, my immediate boss, was embezzling. I knew it but it took me a year to get enough concrete proof to take to the President. After I presented my case to the Pres of the company he said he would look into it.
I had worked there long enough to know how he operated. He would talk to the Police and request an undercover white collar crime detective be assigned to the case. He also hired a private detective to investigate.
It took three years before the VP was called in to a surprise meeting in the big conference room. I imagine he was surprised by being escorted out in handcuffs to the applause of the management team.
Four years from discovery by someone who would report it to the arrest.
Sounds like they relied on lawyers to consul them.
I caught a general cashier at a hotel stealing and fired her immediately. I had all the evidence. She begged for her job ,sob story and all until I said I’d just call the police.
Problem solved.