You are probably correct, but it still seems to be the case that the virus spread is slowing faster than expected even with relaxations of lockdown measures.
I suspect the explanation is complex. It is probably a combination of factors: individual awareness in reducing social contact, northern hemisphere summer, and individual variability.
It's probably not the case that a large proportion of people are immune, but there might be big differences in susceptibility. The examples you mention are either from early in the pandemic where social distancing rules were less habituated, or enclosed environments where transmission is harder to avoid.
I'm just guessing, but this would support the European strategy of initial lockdown followed by moderate social controls if outbreaks become more controllable after the initial surge.