Animal Farm 6.

”[The farmer's] men were idle and dishonest, the fields were full of weeds, the buildings wanted roofing, the hedges were neglected, and the animals were underfed.” P.19

(E) Mr. Jones (the farmer) started to mess up at the wrong time. This was just when he needed to keep the animals happy the most, since they were starting to plot against him and develop their way of thinking, Animalism, but instead he let himself slip and the animals took notice. That's how they were able to revolt in such a small amount of time.