It's up to the reader to speculate how much criminal activity took place in the conversations they failed to retain. I, for one, am certain it was all just brokers gabbing about American Idol.
You realize these are just people, right? People who work at banks are people like you and me. They can use iMessage to talk about whatever they want. Should we assume every single Google employee talking to another person in tech using iMessage was talking about how to subvert democracy or dark patterning a new scam? Or are they talking about what time dinner is, who's picking up the kids today, look at this meme, etc...