I think they thought chaeyoon will commit suicide after raiding the dungeon so they gave him unreasonable wills to keep him alive.
I'll try my best to explain. With so many of them dying, the remaining ones had started to lose hope, despair and write their wills waiting for their impending death. Seo Chaeyoon had lost hope when his friend Dom died. There was no meaning in fighting for justice, no point in holding out. All that awaited them was pain, suffering and eventually death. It was unfair that the strong had to be burdened with this 'sense of duty' to save humanity. So he decided to end his life after all of this was over. His comrades picked this up and started passing on their dying wishes onto him so that he'd continue on living trying to fulfill their wishes. So they made their wishes as ridiculous as possible to buy him time, like squat 3 million times, climb every popular mountain in Korea, find clouds shaped like sharks, etc.
Why does his comrades feom 10 years ago gave him so many wishes to do? Was there a reason for jt? Cuz theres no way they'd just ask someone to knit 100x