what did capitalist do in real life compared to mr.whymper in the book?

Which capitalists do you mean?

stalinism

A solicitor in Willingdon who acts as Animal Farm’s intermediary to the human world. He is “a sly-looking little man with side whiskers.” He visits the farm every Monday to get his orders and is paid in commissions. Mr. Whymper’s business-minded attitude towards Animal Farm, which allows him to ignore the injustices and atrocities committed there, make him a parody of nations that conducted business with the Soviet Union while turning a blind eye to its internal affairs. This character can be seen to be a caricature of the stereotypical capitalist who cares only for profit and ignores misery.

Mr Whymper represented the capitalists (Westerners) who did business with the Soviets. He is a symbol of those men who turned a blind eye on Stalinism and made money by catering to him and promoting Soviet untruths.