Totally non-scientific opinion here, but I think France is now experiencing rapid (uncontrollable ?) spread due to several decisions that were made to keep life as normal as possible:
Schools open as normal with total reliance on mask-wearing in the absence of distancing. No bubbles, no closing classes due to a positive test.
Reduction of the isolation period from 14 to 7 days - purely to increase compliance.
End of WFH as the norm and the majority returning to the office and all the public transport being used
Students returning to hugely overcrowded lecture theatres, no distancing possible (or even expected). They’ve just been told to go to 50:50 teaching.
Workers still following the cultural expectation where you sit down and eat, sans masks, with your colleagues, every day. Where I work, of the 20 cleaning staff (who are responsible for cleaning the door handles, refilling gels etc) were reduced to just 3 a couple of weeks ago: the other 17 had either tested positive or were Isolating as cas contact as they’d had lunch together every day as per normal, all maskless, all round the same table. It’s how I caught it too.
And the biggie ... No restriction on private gatherings, family lunches / Birthday parties / get-togethers all continuing as usual.
Initially the biggest rises have been in younger people, and that’s still the case. There are probably lots and lots of asymptomatic cases amount children too. But inevitably it’s spreading to the older population (no restrictions on family gatherings means they are continuing: it’s the Toussaint holidays just now, plenty of grandparents collecting children in my street last weekend, lots of friends heading off to visit grandparents elsewhere).
I said above that life feels quite normal and nice here. Well, this is the price we are paying for that: 40,000+ New cases in 24 hours.
The Govt will act when the hospital beds / icu beds run out, that’s their only red line.