Why is killing a lion / tiger is fine, but killing a a cow is Mahapaap

I want to know your thought process about this - in the end they are all animals, living organism, but yet killing one is a Mahapaap while the other might not amount to much, not at all if it is hunting.

I was thinking about this very topic the other day after I watched an episode of Upanishad Ganga, where a King had to do prachyit for Gau Hatya because while he was hunting a lion killed one of his cows nearby. That led me to think - well, he was there hunting, intending to kill a lion, but when a lion killed his cow, not even he himself, he had to do prachyit for it.

And I came to the conclusion that: Maybe you don't glorify killing, but if you kill a lion you are actually saving a lot of its future prey from getting killed too, but if you kill a cow - well you are killing the most gentle creature that is vital for human society. Not saying that you go out and kill all lions, because there needs to be a balance of everything.

I am interested in reading what you all have in mind about this topic.