"But that $3 billion represents only a small part of the bank’s takings from just this one scam—customer money to which, by its own admission, it “was not entitled.”"

This is totally incorrect. The best estimate of how much money was made from the fake accounts scandal is... about $2m gross. That's for a pretty obvious reason which is that it is very hard to secretly charge people money and very easy to secretly open an account for them which then goes unused.

Essentially, WF did not really profit from this, it was the employees and officers who were fleecing the company and fraudulently opening accounts to do so.

Branch employees were incentivised to sell products like accounts and cards to customers on the theory that WF profited from such sales. Compensation for the employees was set based on an assumed / historical profit per cross-sold product. Senior management had incentive packages that were also based on that assumed link. But of course that was calibrated based on real accounts. Shadow accounts that are setup but not used by the customer (because they don't know they exist) do not and cannot produce profit for the bank. What the bank would have seen over time was number of products sold going up but profit per product going down. Since the former is a leading and the latter a lagging indicator, it can be a long time before that becomes apparent.

From the point of view of WF, this was the dumbest possible fraud because it didn't make them money. I bet that $2m in account opening fees actually comes from the less experienced crooked branch staff because it seems like a rookie mistake that would lead to you getting caught.

Of course there is no such person as "Wells Fargo", and from the point of view of the branch and management employees whose compensation depended on these cross-sales numbers, the scam worked just fine until they were caught.