Isn't a large part of ethanol it's use as a fuel additive that it boosts octane and is relatively cheap? Compared to leaded gasoline it seems very "green".
Per https://www.eia.gov/kids/history-of-energy/timelines/ethanol...
It looks like it usage of ethanol as an additive started increasing around the same time lead was being phased out.
Granted, we will likely always need to do this, but where was the need at this absurd scale? Most of our heavy industry runs on diesel anyway.
In terms of a use of money it is a good way to subsidize the american corn farmer. Whether you believe that is worthwhile depends on your views of WWIII.