The first is that his visit likely came after a smallpox outbreak; second, it was the time of the year when most people would be inland hunting and gathering. Third, First Nations people were likely avoiding the Lekwiltok raiders.
The passage provides three reasons why someone might have visited during this time period, including a possible smallpox outbreak, the hunting and gathering season, and First Nations people's avoidance of the Lekwiltok raiders.