Why was the light peppered moth able to flourish prior to the industrial revolution before the pollution left dark soot everywhere?

Peppered moths are found around birch trees. Before the industrial revolution the bark of the trees was white in colour therefore the light ones were camouflaged whilst the darker moths stood out. Because they stood out they were preyed upon by birds meaning they did not live long enough to reproduce whilst the lighter ones survived. This meant they could pass on their colour to their offspring as they were more likely to survive