Originally Posted by KingDavid8
I heard that the writers didn't like working with him, and McLean said that if his new show ("Hello, Larry", IIRC) didn't go well, he might return to "M*A*S*H", and they wanted to make sure that didn't happen.
If that was their motive, they didn't do a very good job. It would have been all too easy to announce in a subsequent episode that oops, it wasn't really Col. Blake's plane that got shot down after all. If Blake had been killed by, say, a sniper or a shell that landed on the helipad just as he was leaving the 4077th, that would have presented a much greater obstacle to bringing him back.
In any case, I doubt the producers would have resurrected the Col. Blake character even if McLean Stevenson had come back to them begging on his hands and knees. (He walked out on a five-year contract, remember.)