My interpretation: Man caused the extinction of the mammoth. These mammoths were on an island, protected from man, but eventually succumbed.
Most of the large mammals in North America mysteriously became extinct after the arrival of native Americans.
They were also isolated from diseases that may have killed the others. I don't think the human population was large enough to kill off all the things that went extinct...something else happened.
Surrounded by water on all sides, they would have been a few degrees warmer than those on the mainland.