Kids are, for lack of a better word, dumb.
I know it's not their fault, and as someone who once unscrewed a light bulb and licked the inside of a lamp while it was still plugged in just because I could, I'm not going to act like I never did stupid things when I was younger. (Fourteen years old is technically "younger," right?)
The Internet is filled with examples of what can happen when you combine this natural naivete with equally unchecked wanderlust, and many of those examples end up with little kids stuck inside claw machines.
I can't say I blame them -- I didn't find out the machines were rigged until a decade after I spent way too many in quarters to eventually win a tiny stuffed horse at a bowling alley.
I can't tell you what was going through the mind of the girls in this video, but I assume it went something like this: The toys (and later, my sister) are in the machine. I am outside the machine. The machine won't bring them outside, therefore I must venture inward.
I don't know if the second girl was able to escape, or if she's doomed to lounge in a plastic box surrounded by stuffed animals for eternity, but I'm optimistic they were able to figure out a way to avoid the second outcome.