HSBC was fined $1.9 billion for processing (not profiting) $881 million + $660 million. Their profit was probably only a few percent of that. But even if they simply took all $1.5b as profit, they still were fined more than that.

You might say they probably laundered more money than that. You're probably right. But it ain't what you know, it's what you can prove.

Assuming the bank profits a few percent, a $1.9 billion fine wipes out the profit from 10s, maybe 100s of billions of laundered money.