If you wanna go by their bad moments I can easily bring up Olive getting punched in the head repeatedly and getting rocked by 40 year old, steroid gut Chandler.
I favor Ilia but Olive might be able to have a chance if he doesn't go for those stupid, defenseless flying knees with his hands down and applies a grappling heavy game and creates some scrambles and maybe latches onto a sub in midst of all the chaos.
Ilia is short and this has resulted in him getting caught with head kicks in the past and Olive has some good kicks so that could also be on the table.
The best thing Olive can do is make it to round 3. I think his size advantage could be valuable if it goes that far.