A lot of generalization and supposition in the above.

Adding charging stations may require grid upgrades, but its a slow and steady requirement you can do neighborhood by neighborhood. Depending on the neighborhood, it may not be required, be minor, or be massive. It all depends. Making sweeping generalization about power generation, a deeply localized utilty, is a poor choice.

In my locality and most of my state, a large amount of charging spots are going up in front of common retailers with no clear utilty work. Our grid is currently fully able to bear the added load.

As to who pays for it, the current system seems to work, and will only improve as more cars go electric. The most effective method seems to be a mesh of private/public investment. Public for grid sizing, power supply and sometimes space for the charger. Private cost of wholesale power, charger install and maintenance, interoperability and paymebt processing. The Private entity takes the gross profits in the above, paying for power and any split with other private entities. The public has its costs covered and has a net positive public good added.

It is not that complicated to install charging infastructure 2 chargers at a time. It seems pretty apparent that retail spaces at least in the US are over built powerwise, and can largely handle the addition. Its why many grocery stores have them popping up suddenly in urban areas.

As to the cleanliness of energy, one large pollution provider is overall more environmentally friendly than millions of small ones. They can also be regulated and inspected in a way millions of small ones cannot be. Centralized generation of power for cars via electricity, of any source, will be greener than millions of cars burning gasoline. Always. Shifting the load to renewables as well is the right answer, but any shift here is good.

Stop saying this is a "massive infastructure challenge" when its actually a small and steady challenge occuring thousands of times. Small things done over and is the massive part, and they are very doable today, in the US and the EU.