His income fell, and he had to look for other sources to cover costs. That basically describes the challenge low interest rates pose to bank profitability. For some time the impact on banks of falling interest rates seems to have been ambiguous. On the one hand banks' interest margins have been compressed.
On the other hand, lower rates may simultaneously have had a positive effect by supporting banks' lending volumes and trading book valuations. But evidence shows that since 2020, the already slim bank interest margins have been squeezed further. Lending growth has not been able to compensate that, and this resulted in a drop in net interest income.