Why were the experiences of the earliest settlers at Jamestown and at Massachusetts Bay so different?
Jamestown, the earlier settlement, almost failed whereas the Massachusetts Bay Colony was solid for its beginning.
Jamestown (1603) was founded as an agrarian settlement. It was funded by British merchants who were looking to make a profit in the New World. But for several years the colonist struggled just to survive and what little they sent back to England did not cover costs.
The Massachusetts Bay Colony was founded by a group of Puritans, mostly middle class Englishmen, who left England for purely religious reasons. They were self-funded and were not beholding to any investor group in England.