The government receives revenue from gas taxes, and they spend money on EV incentives and renewable energy, so in a way the taxes do pay for reducing CO2 emissions.
AFAIK the fas taxes are mostly paying for infrastructure (mostly roads) and often they often don't cover the costs. This is the reason why some countties are introducing similar charges for EVs. Now you could argue it's a subsidy, but to mean it seems more like an oversight.