All the shitty things that have ever been done to us as individuals or communities came from other human beings.
Animals are innocent.
Mathematically, it makes way more sense to have stronger feelings for animals than for people.
This, but i wanna add it it since the OP example is poorly thought out at best.
Lets take things into perspective here for a moment.
There are murders every single day in the US and around the world. The TV news has fetishized and manipulated death and disaster from humans to other humans to the point where when someone dies it ends up being less of an raw emotional internal response and more of an every day thing now.
The lion in the OP example isn't "some fucking lion" either, but rather a decently well know scientifically studied protected animal that was illegally hunted down for sport. If it was an accident, if it was any other animal, whatever, this wouldn't be as big an mainstream as it was. It caught on because of the internet and mass media.
if we are talking race here, you have a huge interweb of bs and mess revolving around police and "whataboutsims" and "what if he was a thug" and all that nonsense that ends up taking up the tv news because everything relating people to other people is political to the highest degree especially when race is considered (even though it shouldn't be that way). It isn't that way when it comes to animals, especially this one, which is why the reaction was a visceral and as horrifying as it was. When was the last time someone died on the news that wasn't a celebrity and people on tv who weren't family cried? Lets not even forget that the specific cecil thing wasn't isolated to Kimmel. As much as I don't like the guy myself, he was part of the sweep of emotions and it got the better of him.
If we weren't so used to death and police shootings and mass shootings and people being the worst of the worst of scum then I honestly think that more people would be hurt and more people would be crying.
But sadness, empathy and sympathy aren't some contest nor is it some finite resource.
The masses' emotions don't make sense a lot of the time. If we handled our emotions based on "order of importance" then the world would be a damn well better place, but the fact of the matter is we fucking don't. Crying about Cecil isn't some racist move from Kimmel just because he didn't cry during a police shooting of a black child. When the news and the media and the internet take the emotion away from a situation, what would you expect to happen? But I guess we should only ever cry when the worst of catastrophes and be steelfaced otherwise, right?