Fraiser Island is all sand, so the rental would specifically be for "off-road" use.

I'm sure the OP's use of the clutch played a role, but I suspect the OP wasn't the first and it's had its share of wear and tear.

The big question is what specifically does the rental contact state.

I would encourage the OP to dispute this. Worst case scenario if the OP is held responsible in some form per the contract, it's of my opinion the OP's liability should be limited to a depreciated value based on wear and tear of use by previous renters.

Last but not least, I have heard of one other outfit (in another part of Australia) that does off-road rentals where many overseas "customers" have encountered similar issues based on several second hand accounts.