I would suggest that because
I would suggest that because diesel and TDI is already popular, that makers of those vehicles don't need help. The situation with CNG is a little different because while natural gas is "everywhere", it isn't widely available in a form suitable for refueling a CNG car. In fact the CNG refueling infrastructure is much worse off than the EV refueling infrastructure. The DoE recently floated some grants (?loans?) to several companies to build better CNG refueling infrastructure.
As for the future availability of fossil oil ... er ... world oil supplies have already hit peak oil ...