The primary reason settlers left Massachusetts for Rhode Island and Connecticut was that they disagreed with the strict Puritan rule. Many people who settled in Rhode Island, such as Roger Williams, sought religious freedom and the ability to practice their beliefs without the rigid constraints imposed by the Puritan leadership in Massachusetts. Similarly, some settlers in Connecticut, like Thomas Hooker, were motivated by a desire for greater political and religious freedom.
While factors like land availability and conflicts with Indigenous peoples were also significant in the broader context of migration and settlement, the fundamental driving force for many of these early settlers was their quest for a more tolerant society that allowed for diverse beliefs and governance structures.