I was thinking the same thing. From a scientific standpoint, the driver might as well not have worn a mask at all.
But then I thought about it some more, and I'm willing to give the driver the benefit of doubt. Lots of people don't seem to have a good understanding of the mechanism of how masks prevent the spreading of COVID-19. The driver may not have realized that all the COVID-19 virii that he breathed out before he put on the mask stick around & potentially infect his passengers.