Cats are solitary hunters by nature... all cats with the
exception of lionesses are.. and sometimes lionesses also hunt
alone.. it's in their nature.
Dogs are pack hunters... that is why strays always band together
and they will hunt together.
If you have 1 dog, he'll look to the owner as the Alpha or dominant
leader. Cats are different.
That's why your hamster got killed.
If it was a pack of dogs, and you tried to defend your hamster from
the attacking dogs, you'd probably get killed too.