It's not uncommon to see donations of 5k USD and up in a single transaction. And oftentimes all this person gets in return - that is, if the camgirl.. apologies, streamer notices the sum come in at all - is a "you're so sweet thanks!".

I just can't understand what they're hoping to get out of handing away so much money. Do they believe theirs will be reacted to differently? But why them? It's just so irrational!

I think it makes them feel appreciated when others are thanked as they now feel that they are part of the group (who is being thanked). Their individual donation doesn't need much praise if any. I agree with one of the other posters that it is related to loneliness. I could be mistaken obviously.