What& #39;s the explanation for France covid-19 deaths being relatively low while number of cases is exploding?

Is it 1 the lag between infection and deaths, 2 the fact that it& #39;s mostly infecting young people (and if so how does it not eventually spread to older people), sth else?

Reason 3 would be treatments getting better.

Some talk about how the virus itself is evolving to become less dangerous but I think that& #39;s a wrong reason bcz (selecting for) these kinds of changes don& #39;t happen at the scale of one year.

Same pattern in Sweden; it feels weird to me I really want to understand it...