Credit cards are bigger than you think. The CM5 is smaller (55mm x 40mm) than credit card (85mm x 54mm). You could almost get two on one credit card.

I always thought it was deceptive to compare regular Pi to credit card. But I just checked and credit card is almost the same size as regular Pi.

You're forgetting the third dimension, which comes in at 4.7mm. That indeed makes the CM5 much larger at multiple times the volume - if you want to be pedantic that is.