Gas turbines operate efficiently at constant output, which a hybrid-drive system with storage can manage. They only need to kick out enough power, on average, to keep the storage system fully charged. Batteries and eletric motors can handle both high-demand accelleration, and regenerative braking. Since the turbines are running at a very constant range, and can be rated to average out power load inclusive of idle times, they can be designed for optimum efficiency within that range. Or that's the theory.

There've been other gas-turbine automobiles, including some prototypes built in the 1960s. A friend of mine test drove one, claimed it could lay a patch (spin the tires) at highway speeds. Though my understanding is that in direct-drive applications (such as that), turbine lag is an issue.

The exhaust also runs quite hot, and turbines typically emit a lot of NOx (nitrous oxides), what you get when you run atmospheric nitrogen through a high-temperature field.

Much anecdata here, apply salt liberally.

For anyone interested in turbines and cars, there's a delightful episode of Jay Leno's Garage about a Chrysler turbine car:

https://www.youtube.com/watch?v=b2A5ijU3Ivs

He talks extensively about how it works, what it's like to drive, and the various difficulties that resulted in it never entering mass production.

It sounded like a gigantic loud vacuum cleaner even just idling, and gave the impression of straining mightily to achieve even mild acceleration. Fuel consumption was TERRIBLE.

The large volume of very hot exhaust you mention is your clue that the thermal efficiency of small gas turbines is poor to dismal.

I assume the CO2 values factor in the electric only range.