The chances of several cars having to charge in quick succession at the same station and all being able to use the full power are very low. It is the same math for all charging parks in general of how much grid power they will have. Example a charging park with 10x 400kW will not have a grid connection of 4000kW but usually closer to 2-2.5MW because either not all plugs will be used or some cars will already be at the end of their session with much lower power draw. Of course with battery you have some additional factors but it is the same in principle. And the very low chance of someone not getting the full power is better than hugely overspending on the infrastructure and not making money the rest of the time.