The challenge level of the cave troll is not low, normally higher than that of the Dead Stinger Spider, but it's severely injured right now. The most obvious injury is that it only has one arm left, in addition to countless other wounds large and small, its intestines are nearly spilling out of its stomach...
Of course, these injuries look serious, but for the cave troll, trolls generally possess strong regeneration ability. It could fully recover in less than an hour, a complete recovery, not just scabbing over. However, regrowing an arm might require a long rest.
If the cave troll had a bit of rest time, Leon and Evil Wolf, who remained in human form, would definitely have some trouble handling it, but they surely wouldn't give the cave troll a chance... Not that they wouldn't give it a chance, but because the cave troll immediately lunged at them upon sighting them, desperately needing food to fill its stomach.
