If there is a classless society which strives to treat everyone the same, why are the pigs taking the lead? within the ranks of the pigs, which three are predominant? why?

I’m assuming you are talking about animal farm. The three pigs take the lead, because they think that they are superior to the other animals. Due to them being more intelligent than the other animals. The three predominant pigs towards the beginning of the book are Napoleon, Snowball, and Squealer. Towards the end the only two predominant pigs are Napoleon and Squealer, because nap and snow competed for the top leadership position and Squealer turned black into white and did all the talking for nap. Snowball than is run off the farm and the only two are left to "lead" the farm.