"simply ban combustion engines and gas boilers" - there's nothing simple about this
We probably shouldn't talk about an outright ban. There are a couple of places where we may need to say, in your niche, those don't work, so we'll let you continue using it. We'll worry about those later. Let's stop the vast majority of cases first. Then we start worrying about the niches.
The above covers about 98% of all car sales: you can make an EV and if everybody else is also buying EVs that creates enough demand for things like chargers that they will automatically go in to fill the demand.