Nuguse is the one who broke it, and I'll say it: Nuguse is more talented than Cragg was. Also, Bosley broke Nuguse's record, and he had 4 years of altitude training, and was the top recruit in his class. Ky Robinson crushed the 5k/10k double last year as a junior. Nico Young has been heralded as the next great distance runner literally since I started following the sport.
I think pretty much everyone accepts that the shoes are making athletes faster, but for guys like Las Heras and Quax, I think the altitude + Mike Smith + training with teammates that can run sub-7:40 makes a WAY bigger difference than the shoes. Las Heras had 4 years at Wake Forest where he had super shoes, and he was clearly a very good runner, but nothing close to national class. Less than 1 year later, the shoes haven't changed, but now he's running 7:37.