Philadelphia won and now their eating horse manure?

I don't understand the craze with eating horse manure if your team wins the Super Bowl. I am sure we all saw the online news of all the crazy things Philadelphians were doing because their team upset the patriots dynasty.
Being from Seattle and a die hard Seahawks fan, I was partly glad to see the end of the Patriots grip on almost all championships in the last decade.
But why conduct a festivity by eating horse shit? Whats going on Philly?
The city of Philly even went so far as to cover all the posts in city limits with oil so that people would not climb up on them.
And this one guy outside the Minneapolis stadium was eating horse shit because the eagles won????
You would think that would be if you lost a bet?
Funniest thing I heard all day was the question: what would happen if the Browns had won the Super bowl?