Complex sentence: Early South Asian migration to Canada was primarily a Punjabi Sikh project but within this group of early pioneers there were Hindus and all were referred as "Hindoos" by the White British Columbians.
Split into simpler sentences: Early South Asian migration to Canada was primarily done by Punjabi Sikh individuals but within this group of early pioneers there were also many Hindus. All South Asian migrants, regardless of religion, were referred to as "Hindoos" by the predominantly White British Columbians.