Who is Norway’s cross-country ski superstar 'King Klæbo'?

Johannes Høsflot Klæbo is Norway's powerhouse cross-country skier who set another record on Wednesday by winning his fifth gold medal of the Milano-Cortina Winter Olympics. He's now just under highly decorated U.S. swimmer Michael Phelps on the list of athletes with the most Olympic golds. So, what makes him so good?