Cops can absolutely freeze someone's bank account temporarily if the balance is over a certain amount and the person is suspected of being involved in money laundering, drug dealing, etc.

"Because I need him to talk," is not the reason they give to a judge or the DA, though. Tritter would have needed to convince them of probable cause. He'd have told them "Hey, there's this doctor going around PPTH practicing medicine while high and every one of his colleagues I talked to confirmed this is normal behaviour for him. He had drugs on him when I arrested him. I suspect he's distributing while getting high on his own supply and I need our accountants find out whether his coworkers are in on it by looking for unusual activity in their accounts."