This happens also with automotive companies. Peugeot has its own bank, which lends money to people buying peugeots. The big difference: is not circular. The bank is a bank, the OEM building cars build cars.

The bank makes money by lending and cashing interest.

The car maker by selling for profit.

The money goes from bank to OEM, and not the way around, no circle.

I do not know the specifics of Boeing though.