Based on this data, 48.6% of oil was used on the read. If we assume that about every other car becomes electric, that could cut the total oil demand by about 24%. That’s actually quite significant, but obviously it will happen so gradually that the oil industry should have enough time to adjust.
Eventually most cars will be electric, but even that won’t destroy the entire oil industry, because there are still many other uses for oil. It takes a while for various other industries to shift away from burning oil and gas, but when that happens the oil industry will be totally screwed.