Getting to the final of any event is tough. For the best guys though, making the semifinal is usually just a formality. But today, Jakob, Habz, and P. Koech didn't get through.
Jakob didn't have an outdoor season leading up to this, but indoors he broke the 1500 and mile world records (in the same race) and won the world championships in the 1500 and 3000. Even though his fitness was unknown going into the race today, him not making through the first round was still a surprise considering his accomplishments over the previous few years.
Habz is the fastest man in the world this year and has won 2 diamond leagues (technically the one in Paris wasn't a diamond discipline, but it was during a diamond league meeting and had a diamond league quality field.) Even if his championship pedigree isn't great, he seemed to be on another level earlier this year.
P. Koech also won a diamond league this year, outsprinting Josh Kerr, and is the second fastest man in the world this year. There was a point after the London Diamond league where he was probably considered the favorite for worlds. Unfortunately, he fell on the last lap and wasn't able to recover to be top 6, and since nobody else was to blame for the fall, he couldn't get through on protest and went home devasted with Jakob and Habz.
Myers also didn't make it, but he hasn't quite shown some the things the other 3 have.
You could expect this level of causalities during the semifinals because making the final is so brutal, but to see it in the first round is nearly unheard of. 3 titans out already.