I predicted this to Sunken Civ as far back as the first discovery of a DNA potential carcass. And followed up over the years with dire predictions of where this cloning was going in the animal world.
It might have even been before Jurassic Park. What would be a logical purpose for all the cost and research to bring back an animal that lost the evolutionary race? Dolly the sheep was at least a benign creature if it worked out.
The last mammoth remains are not as old as the Great Pyramid. The fact is, mammoths died suddenly and simultaneously for the most part -- the surviving lines were isolated, somehow protected from the fate of all the others, and genetically quite narrow due to that isolation. They didn't go extinct because they weren't well adapted, according to the autopsies, they lived on buttercups when nothing else was available (like Snickers Bars).