The Valencia Half Marathon in Dec. 2020 Kibiwott Kandie reduced the HM WR by 30 seconds, and 4 men in total beat the old record in the same race. https://www.bbc.co.uk/sport/athletics/55206158

In the words of Jen Barber "the shoes!"

> There is a ban on any shoes that have a sole thicker than 40mm. > Kandie was using Adidas shoes that have 39mm of foam.

There's also the fact that African runners train differently, and even their gait/pose is slightly different with their chests thrust out slightly.