Manufacturing actually applies to both types of cars. Steel is made from coal, limestone, and iron ore. Making these requires burning a lot of coal for heat. So, I kind of discount manufacturing. Also, in an ICE car, you still have a lot of wiring. Alternator, starter, and all electrical components.
They are moving away from Lithium Cobalt to Lithium Sodium batteries. Tesla gets their lithium from Nevada. It does require strip mining. So does copper and some other minerals. Lithium can also be extracted from sea water. Cobalt is mined in Africa with child labor, thus getting away from cobalt and switching to sodium which is in salt and sea water.
An EV assembly line is completely different from an engine assembly line. This is what is holding back the big three.
I think if they want to get rid of "fossil fuels" they need to fix the power grid first. Solar and wind can only go so far without massive battery or some type of storage for night and when the wind doesn't blow. Nuke plants are really the only way to replace coal and natural gas. They can work 24/7 for 30 years or more without refueling. Smaller nuke plants cannot "melt down" like a larger one. Also using thorium instead of uranium will vastly decrease the decay life to safe levels after use. No need for very long term storage. Once the grid can produce about twice the power as today's grid, then concentrate of solid state batteries that can charge in 5 minutes and go almost 1,000 miles (Toyoda's claim on a test car they made recently).