More than the psychological factors which you talked about (i.e. that people are weary or governments have declared triumph over the virus - which is false concerning France for instance), I think that the main reason is the seasonality of the disease (which is a well-known phenomenon observed for other diseases, as far as I know).
I think one can see it observing Sweden's case: the number of infections (and deaths) had slowly diminished starting from may (not as fast as in other European countries after the lockdown) and the deaths have been rare (1 or 2 per day) until now. But now as everywhere else infections are increasing.
Furthermore, it is not really credible that most European nations have had coincidentally a resurgence in cases at the same time. As far as I know, it is often quite complicated right now to move from a country to another at least in my case (France), so I don't think this can be explained by spreaders from a country to another (and there were still clusters at that time (early September), so why would transnational spreaders be necessary to sparks infection anew ?).
More than the psychological factors which you talked about (i.e. that people are weary or governments have declared triumph over the virus - which is false concerning France for instance), I think that the main reason is the seasonality of the disease (which is a well-known phenomenon observed for other diseases, as far as I know).
I think one can see it observing Sweden's case: the number of infections (and deaths) had slowly diminished starting from may (not as fast as in other European countries after the lockdown) and the deaths have been rare (1 or 2 per day) until now. But now as everywhere else infections are increasing.
Furthermore, it is not really credible that most European nations have had coincidentally a resurgence in cases at the same time. As far as I know, it is often quite complicated right now to move from a country to another at least in my case (France), so I don't think this can be explained by spreaders from a country to another (and there were still clusters at that time (early September), so why would transnational spreaders be necessary to sparks infection anew ?).