I somehow doubt that your neighbors launched a brute force attack against your router and discovered your 8 character password.
I really don't like this image because it pretty much works by making the reader feel stupid. This reader then believes that the image is entirely correct and follows its advice, even when it's bad.
The reason you've all been told to use complicated passwords with capital letters, numbers, and symbols is because it makes the attack exponentially more difficult to run.
Cracking the password "correcthorsebatterysample" would take forever to crack. However, this comes from the length. The word "correct" would only take 2 seconds to guess. "troubador" would take 22 minutes. "Troubador" would take 8 days, "Tr0ub4dor" would take 39 days, and "Tr0ub4dor&3" would take 4 thousand years to guess. It's easy to see how merely capitalizing letters and substituting out some letters for numbers makes a password virtually uncrackable.
[1]Anyway, my point is that this poster is correct but for the wrong reasons. It's not easier to guess passwords with tons of symbols, it's much, much harder. The reason "correcthorsebatterystaple" is a better password is purely because of length. "C0rr3cth0r$eb4tt3ryst4pl3" is a much, much more secure password.
