Having considered the possibility at the end of the second season, Cleese left the Flying Circus at the end of the third. He later explained that he felt he no longer had anything fresh to offer the show, and claimed that only two Cleese- and Chapman-penned sketches in the third series ("Dennis Moore" and the "Cheese Shop") were truly original, and that the others were bits and pieces from previous work cobbled together in slightly different contexts. He was also finding Chapman, who was at that point in the full throes of alcoholism, difficult to work with. According to an interview with Idle, "It was on an Air Canada flight on the way to Toronto, when John (Cleese) turned to all of us and said 'I want out.' Why? I don't know. He gets bored more easily than the rest of us. He's a difficult man, not easy to be friendly with. He's so funny because he never wanted to be liked. That gives him a certain fascinating, arrogant freedom."  The rest of the group carried on for one more "half" season before calling a halt to the programme in 1974. The name Monty Python's Flying Circus appears in the opening animation for season four, but in the end credits, the show is listed as simply "Monty Python". Although Cleese left the show, he was credited as a writer for three of the six episodes, largely concentrated in the "Michael Ellis" episode, which had begun life as one of the many drafts of the "Holy Grail" motion picture. When a new direction for "Grail" was decided upon, the subplot of Arthur and his knights wandering around a strange department store in modern times was lifted out and recycled as the aforementioned TV episode.  While the first three seasons contained 13 episodes each, the fourth ended after just six. Extremely keen to keep the now massively popular show going, the BBC had offered the troupe a full 13 episodes, but the truncated troupe (now under the unspoken 'leadership' of Terry Jones) had come to a common agreement while writing the fourth series that there was only enough material, and more importantly only enough enthusiasm, to shoot the six that were made.

Answer this question "what was the reaction to the circus closing?" by extracting the answer from the text above.
there was only enough material, and more importantly only enough enthusiasm, to shoot the six that were made.