The whole thing is largely explained by the fact that social distancing started to have an immediate effect in new infections delayed by the 1-2 weeks for the symptoms of those infections to be expressed.
Vigorous social distancing certainly has decreased the transmission rate. My statement was intended to note that a further reduction in the transmission rate may be possible if the virus has a seasonal aspect to its transmission. Whether or not the warmer season has a substantial effect is unknown presently. It will be interesting to see how a country such as Mexico (my understanding is they are not taking substantial actions) fares during the pandemic.