Many of those 8 million had something unforgettable and bizarrely enlightening to share with their friends, or not, as the case may be (if they don't really have any friends). I would say that you underestimate that monkey, he has brought a lot of happiness to a lot of people and he fully deserves his own reality TV show. So, yep, he has changed the world.
I much prefer the world to be changed by things like 2048, which is like an online version of the Rubik's Cube for our times.
Contrast with the world-changing ways of the politicians. Bush, Blair and co worked very hard to take the world to war, yet, ultimately, they lost and it was all a complete waste of time.
"Changed the world" could have a variety of meanings. Taken literally, it could mean "altered or affected the world in any amount." Going with such a strict definition, nearly everything changes the world.
The other extreme, the one people frequently have in mind, is "to change or alter many parts of the world very directly", such as the invention of flight.
However, a better phrase for the feeling in developer circles I think would be "touched the world." Doing so, with the internet, is easy. Like building a public bench in a city park, many people may gain small enjoyment from it, and as the one who built it, all that small joy brings you lots of excitement.
Think about it like this:
If the creator posted a link on the page for a worthy cause, he has the audience necessary to make a huge difference. Whereas if you were to start from nothing and try to create impact, it would be a major uphill battle.
The hard part is reaching enough people. He has already done that.
Another way to think about it:
Richard Sherman is a cornerback for the Seahawks. Is he having an impact? Well, they just signed him to a $58 Million contract. And part of what he does with his money is fund the The Richard Sherman Family Foundation whose goal is to help as many kids as possible have adequate School supplies and clothes.
So does Richard Sherman change the world by intercepting passes and talking trash after playoff games? You bet he does.
People who have the platform to change the world are more likely to, in either a positive or a negative direction.
https://www.youtube.com/watch?v=6DBuk91phkI