Complex sentence: Waterhouse had connections with wealthy Quaker industrialists through schooling, marriage and religious affiliations, many of which commissioned him to design and build country houses, especially in the areas near Darlington.
Split into simpler sentences: Waterhouse had connections with wealthy Quaker industrialist through schooling, marriage and religious affiliation. Many of these Quaker connections commissioned him to design and build country houses, especially in the areas near Darlington.