I think the more useful standard here is "knew or should have known". They would have had to have been literal children to not ever hear that money transfer services could be useful to scammers. So assuming the executives were actual adults, they either knew or should have known that they were party to and profiting from large-scale fraud.

For what it's worth, the FTC did not "charge" them with anything. Walmart is being sued for some pretty specific violations not of "regs" but of laws: https://www.ftc.gov/system/files/ftc_gov/pdf/1823012WalmartC...

Walmart will have their day in court, and they certainly can afford plenty of lawyers. I have no concern at all for the well-remunerated executives at the top of this business, who will face no legal consequences for their personal profit from hundreds of millions of dollars in fraud.