Poor people don't choose to not support their communities. They've been put in a position to be forced to "choose" between supporting their local store vs having a warm, safe(ish) place to sleep for their families.
It is a situation that snowballs, but even originally when foreign goods started coming in, people didn't consciously choose to not support their community. They were just doing what consumers do, which is choose to purchase at the best (lowest) price they could find.
But due to information asymmetry and limited ability to analyze and understand the consequences of each and every purchase, there was only one inevitable outcome, assuming goods and services are allowed to be transported between borders.
