Cigar blowup

I was smoking a Nub the other day, and a little more than 1/2 of the way through it developed a sort of bubble on one side where a small section of the cigar wasn't burning. I corrected the burn, but the swelling soon increased around the entire cigar to a length of about 3/4" from the foot. Imagine dipping a cigar foot first into water and holding it there until it was swollen like a sponge in that area by a good 1/8-3/16" in diameter. Then the cigar slowly ruptured down the length starting at the foot, almost like a fault line ~1/16" deep, and the wrapper split in several places and eventually fell off. I tried everything I could think of, but the cigar finally became unsmokeable.
I had stored the cigar in a tupperdor with 65% beads for about a month before I smoked it. There are some 20 other cigars in the container, so I'm concerned that there might be a problem with my storage.
Does anyone have any ideas about what caused this and what I could have done, if anything, to prevent the final result of having to toss the cigar before its time?