Petrol protests event fires even if there are no gas powered cars

As you can see in the images, I am collecting zero dollars in revenue from the petrol tax because everyone is driving an electric car, and yet the petrol protests event is about to fire.

Your petrol tax is forcing people to drive an otherwise more expensive kind of car. There are some who might resent that.

They are all electric. Or banned.

Yes, the electric car being more expensive. The reason the petrol tax increases the transition is because it prices petrol-powered vehicles out of the market.

But if nobody is paying the tax because of zero revenues then it’s not much of a base to create protests now is it

You are raising their cost of living, by forcing them to buy more expensive cars. That is the basis of the protests. The fact that they aren’t paying the tax is irrelevant, because you’ve still made the price of transport necessarily more expensive.

But if everyone has switched to electric cars, electric cars would become the cheaper option due to economies of scale and the fact that it would be very hard to buy petrole, with or without taxes. People fighting for petrole cars would be the ones with money

Yeah that doesn’t look like a bug! your petrol tax forces people to use electric cars. You should just cancel the tax if you have no revenue from it.
You’ll see the protests will stop on the next turn after you cancel, and eventually petrol cars should start coming back.