500kg would still be huge size advantage for a ferocious animal that can defend hmself and -unlike most crocs large preys- have no problems move/fight in water
Btw hippo weight is bizzarre, they have huge weight range because males never stop grow, so you can have young adults much smaller (being as you say not much bigger than females) compared to huge old adults
If you look average weight hippo seems much smaller than white rhino, but when you look for max weights claimed for both species they reached about same size (theory is 4500kg or 4.5Gustaves
)
As soon male hippo grow enough to touch 2000kg Mr.Gustave would do the smart thing and swim away, he did'nt became old af picking fights with hippos twice his size