It's the chance a non-Marvel character gets a meaningful (Not low hanging fruit street tier) victory over DC, and it has potential to be one of the most exhilarating fights given the source material (TTGL)
I think more importantly Liam wanted him on Death Battle he wanted a joke fight with what I can assume is just a crazy toonforce stomp like Mask/Deadpool. Making it SuperFriends Aquaman of all versions makes it even more of a stomp. Spongebob who can unravel the entire universe, nullify his own vaporization, suck away the entire ocean in a couple of seconds with a reef blower and warp reality and transmutation with song. I don't even recall a single feat this version of Aquaman even has. I don't even think he can force telepathy on sea creatures or that it would even work on a sponge, so there goes that.