Heat waves only became a serious problem in Europe in the last decade. The vast majority of buildings predate the need for air conditioning by several decades - and in plenty of cases by several centuries. The buildings are designed around being livable in a pre-climate-catastrophe climate without needing air conditioning - which is perfectly achievable if you aren't stupid enough to build a city in the middle of a desert.
Adapting all those buildings and streets will take time. Blindly putting AC everywhere and forcing everyone to drive from building to building in an ACed car isn't going to work, that kind of wasteful behavior is how we got into this situation in the first place. You need to redesign the heat management, and you need to start with things like mandating shades to prevent heat from entering buildings in the first place, and planting trees to avoid the heat island effect.
AC will indeed be needed to deal with the final heat peak when outside night temperature is in excess of 30C, but it isn't the one-size-fits-all solution for every heat-related problem it might seem at first glance. If your AC needs to run for more than a few days per year, you've seriously screwed up.