Kumar was killed off because he left to take a job with Obama.
He may have lasted about a year before “leaving” the White House to go to (the third) White Castle.
Oh when will they learn from Pernell Roberts and David Caruso...
To my mind the most famous of these 'premature' actors were McLean Stevenson (Col. Henry Blake) and Wayne Rodgers ('Trapper John' McIntyre) both of whom left M*A*S*H after it's 3rd year and when it was just getting going well.
M*A*S*H only went on another 7 years and earned the cast who stayed considerable amounts in salary and residuals as well as many awards. McLean did end up realizing how well he had killed his golden goose but Wayne has gone on to individual glory as an investor and money manager.