Although Mr. Pilkington and Mr. Frederick do eventually help Mr. Jones try to retake his farm in the disastrous Battle of Cowshed, at first neither one of them do anything when they hear that Mr. Jones has been expelled from his land. There are a couple of reasons for their behavior. First of all, both are "thoroughly frightened by the Rebellion on Animal Farm, and very anxious to prevent their own animals from learning too much about it". With this in mind, Mr. Pilkington and Mr. Frederick initially treat the whole idea as a joke, pretending "to laugh to scorn the idea of animals managing a farm for themselves". They spread the rumor that the animals on the Manor Farm are "perpetually fighting among themselves and (are) also rapidly starving to death". When it becomes evident that this is not the case, they "(change) their tune and be(gin) to talk of the terrible wickedness that now flourishe(s) on Animal Farm...it (is given out that the animals there "practice cannibalism...(torture), and (have) their females in common". Mr. Pilkington and Mr. Frederick are so busy trying to keep their own animals in line by discrediting what happened on Manor Farm that they do not have time to help Mr. Jones get his farm back.
A second reason why Mr. Pilkington and Mr. Frederick do not help Mr. Jones when he is expelled from his farm is because "at heart, each of them (is) secretly wondering whether he could not somehow turn Jone's misfortune to his own advantage". Essentially, their first thought is for their own possible gain; they really don't care about Mr. Jones and what has happened to him (Chapter 4).
Mr. Pilkington and Mr. Frederick do not help Mr. Jones when he is first expelled because they were wondering if they could turn his misfortune to their advantage.