Final answer:
The Middle Colonies' ethnic and religious diversity stemmed from their Dutch and Swedish origins, the English colonial expansion strategies after neglecting the area initially, and the founding of havens for religious freedom like Pennsylvania.
Step-by-step explanation:
The Middle Colonies were the most ethnically and religiously diverse of the thirteen original colonies because of the influence of their Dutch and Swedish origins. This diversity emerged during the period when the English focused on developing their New England and Chesapeake colonies, allowing the Dutch and the Swedes to settle in the mid-Atlantic region.
After the English takeover in the early 1680s, the transformation of New Netherland into proprietary colonies like New York, New Jersey, Pennsylvania, and Delaware led to a significant influx of diverse populations and economic growth. The establishment of Pennsylvania as a haven for Quakers under William Penn, who practiced religious tolerance, further contributed to the diversity. The resulting heterogeneous society was marked by little civic consciousness but allowed for pragmatic, accommodative, and tolerant interactions among colonists.