what happened just as snowball had the animals agreeing with him

I'm assuming you mean what happened to Snowball's plans for the windmill after just about all of the animals were in agreement. Well, Napoleon put an end to the plans in a very insulting way.

"One day, however, he arrived unexpectedly to examine the plans. He walked heavily round the shed, looked closely at every detail of the plans and snuffed at them once or twice, then stood for a little while contemplating them out of the corner of his eye; then suddenly he lifted his leg, urinated over the plans, and walked out without uttering a word."