I blame the schools. But shame on Morgan Stanley for only hiring minimum wage financial analysts. At least make sure they had a C- or better in Intro To Business Math For Dummies.
The highest concentration and number of EVs in the US is in California. California's grid is not 72% fossil fuel as laid out in the report, which used national numbers instead.
Even if you assume there was an unrealistic uniform dispersal of EVs in the US, the average efficiency of the modern EVs is higher than the modern ICE vehicles. Less power per mile means less CO2 in general. ie - strip out the battery and electrics, put in an i4 motor, and a typical EV would use less gas as well. But EV propulsion itself is less lossy on top of that. Hence with wild "MPGe" numbers you see.
This 'Dirty EV' argument is old, and was funded by Toyota at Carnegie Mellon University which doubles as a house of prostitution. They 'proved' a Nissan Leaf is 'dirtier' than a Prius in many states. Problem is, California wasn't one of them, where most the Leafs are. And the fact they used stale data didn't help much either, as the grid is getting cleaner. The average EV in the USA is cleaner than the average Prius.
Here's a brief of the study, and if you look hard at CMU's website, you find:
Corporate Funders
Alcoa, Inc.
Boeing Company
Toyota Motor Sales, U.S.A., Inc.
Where is Nissan? Tesla? GM?