It looks now like the state only okayed bringing the deer to the island back in the 20s, so yes, Wrigley or somebody else probably brought them there for hunting. Whether the bison really came there with a movie crew, the nature conservancy founded by Wrigley has been keeping an eye on them.
If you ever visit the islands in Casco Bay, ME. Off of Portland. You will see all these primarily seasonal homes that are all very close together.
Lots of summer rentals.
Many have to put up deer fencing because if they do not the deer eat all their flowers and any vegetables they plant on these small lots. The deer swam over to those islands. They are close to shore.
Over on the seacoast of NH in the town of Rye the cottontail rabbits have become so numerable that they also have to net any flowers planted around their houses. These are multi million dollar houses within a stones throw from the Atlantic. Most are not rentals. The bunnies are not afraid of people. My son rented there for a couple years. I had rabbits that hopped by me within 4’ and paid no attention.
Again, this is a place the houses are so close together you really can’t hunt. Also, there are not a lot of coyote in this area to keep the rabbit population in check.
NH Fish and Game actually reintroduced the Eastern Cottontail into southern NH to have a natural prey species for the coyote, fisher and bobcats. I have them in my back yard all the time. I am about 60 miles inland. There are predators in my area.
Now, we need something to kill the turkeys. They are everywhere. Too many now. Although they are actually good to have around. They eat thousands of ticks and grubs.