PearlNextDoor
I don't think my thoughts are an exact mirror of yours, but I can see where you're coming from, and I agree to quite an extent.
Whilst I believe that it's up to individuals where they direct their charitable giving, I would always prioritise people over animals, not to say that I wouldn't want to help animals at all.
I think some people have negative experiences of certain people - maybe a large number of the people they know/encounter - and then extrapolate that to all people in general e.g. "No dog would desert me like that" or "No donkey has every designed a machine gun or nuclear bomb" etc.
They will often see all the bad in the world and attribute it to humans (which is usually true - caused by some humans) and then see animals as the innocent victims of a lot of what bad people do. I suppose they think that humans have a voice and agency to change things (theoretically maybe true, but practically very, very far from it for a great many people) whereas animals have nobody to speak up for them. Also, as many people believe that charity that helps humans is their priority, others may see that and think "XXX get given plenty, but nobody ever cares about the poor donkeys" and so want to even things up a bit, as they see it.
Of course, many people will have many different reasons for giving to animal charities/helping animals - very probably none of the examples I mentioned above. Personally, I believe in helping animals, but I would personally want to direct most of my giving towards humans who are vulnerable/under-privileged/in need.
Then again, we're also members of the National Trust, so although, if I'm honest, we mainly joined to enable us to have fun family days out, technically it means that we direct some of our regular charitable giving to a load of old bricks and furniture.
The people who seem to despise ALL of humanity and ONLY care about animals, I struggle to have much understanding of at all.