I have a small pet theory on animal usage of tools: perhaps animals are watching humans and have learned from our example.
In the past, people believed that no animals used tools. We now have countless examples of animals using tools in clever ways. So our ancestors were completely wrong, right?
Well, perhaps the truth is in the middle: perhaps biologists of yesteryear didn't observe animal tool usage because it was less common at the time.
Perhaps, but also there were fewer biologists in yesteryear, and they didn't have access to a cheap and convenient supply of semiconductor golems with unblinking eyes and perfect memories to watch the birds while the researchers were doing other things.
Perhaps primates might fit this theory, but cockatoos making spoons to fish out seeds from fruit whilst entirely isolated from human contact means it's not a learned behavior and is more clever deduction (birds are smarter than most people think).
Not a biologist though (simply a parrot and monkey lover).
For one thing, only some very specific animal species use tools, and then in specific ways that you need to observe closely to notice.
But also, what makes you believe that our ancestors didn't notice? In ecosystems where they observed that, it might have been so routine and obvious to them that it was not something even worth noting. After all, historically, humans have treated animals similar to people for a very long time (e.g. putting them on trial for theft and murder). When you already have that mindset, a tool-using animal is very unremarkable.
In the past, people believed that no animals used tools. We now have countless examples of animals using tools in clever ways. So our ancestors were completely wrong, right?
Well, perhaps the truth is in the middle: perhaps biologists of yesteryear didn't observe animal tool usage because it was less common at the time.