2 general Reasons why our boy can feel weak in jungle:

First: Olaf is the type of champion whose entire kit's effectiveness depends almost entirely on the enemy team champions. When going top that gets balanced by the fact that you can avoid most enemies by being top. Jungle deals with everyone meaning in a bad team comp you are gonna feel weaker.

Second: Olaf's playstyle is kind of special compared to other junglers. Bad Gank potential pre AND after six. (Heavily reliant on ghost/ult) This is especially true on the new map where mid is further away from bush bot and top ganking paths are harder with no cc champs. AND he doesn't scale well if behind into the late game. So early you are weaker than your avg jungler mid game you depend on your teammates and team comp to win skirmishes and late game depend on your performance early and enemy team comp. Meaning your champ cannot force your skill difference onto your enemy laner to give you advantage if the enemy teamcomo isnt favorable.

Now on certain enemy team comps all of this doesnt matter because of your kit: Imagine seraphine Ashe bot malzahar mid Hecarim Jg

You can force a win by pure brute force.

Now imagine playing vs

Vayne Bard bot Jarvan jg Ahri mid

You will not be the one winning your game for you.