BS...this can happen for several reasons. A dry OR overhumidfied cigar will both do this and what will cause this more than anything is cigars not kept at a constant humidity and constantly shrinking and expanding. The cracked cigar my have been smoked while in a dry stage but it would have to be kept damn dry to crack a wrapper. It also depends on the wrapper as well as how a few other things. Most cigars are fairly 'rugged' but at the same time they are fragile. What they don't like is a lot of change over time. You're better of keeping your cigars in a dresser drawer and relying on room temp/humidity than a humidor that has wild fluctuations.
Most seasoned cigar smokers have at some time over-humidified a cigar(s) and the result is most commonly the wrapper at the foot expanding and cracking but this can also happen in the middle of a cigar. That's the tell tale sign of over humidifying. Your filler is expanding. If your cigar is overhumidified ( and I am of the camp of 65%-68% humidity ) the short term consequences are FAR greater than underhumidifying. That has a longer term consequence but neither underhumdifying or overhumidifying is as deterimental than the roller coaster of the two.
When overhumidified the filler expands, creating stress or pressure on the wrapper that holds it together. No biggee. But if you let it go, it will break the wrapper. If you can't keep a level humidity the filler/binder expands and contracts with the humidity, eventually breaking or cracking the wrapper. Simple concept. Put a dry sponge in water and it...expands. It dries up, it contracts. Heat expands. Cold contracts. If you don't get these concepts then read no further.
Let me make this clear. For a smoker that buys a few cigars or even a box..room temp and humidty will show no noticable effect over a few weeks or even a few months. Most people control their home environment with air conditioning. Yes, your house is a big humidifier/dehumidifier. Now, I wouldn't keep them in my car in Phoenix in August or Wisconsin in January mind you, but room temp over a short period generally won't trash them with just a little bit of care. I'm not talking about long term ( 1 year+) or aging which is a whole other ballgame. I digress.
Cigars can also burn unevenly if you smoke them too fast. Personally I like to smoke at home, on the porch and enjoy a smoke. BUT, if I smoke in a sociol setting like a bar, I tend to smoke faster. That will blow up even a properly humidified cigar and for sure an over-humidified or upper end humidified cigar. Heat expands, right ? A cigar can be kept long term, between 65-72% humidity but 72% is the high end. Forget that notion of 68-72. Even the best cigar shops can't achieve that. Mother nature can't even do that. So what is the best humidity level ? Is it not 70% ?
Yes if you can absolutely maintain that without upper peaks. I'd rather protect myself from the upper humidity peaks than the lower therefor 65% is my goal. That way, if it jumps because of the ambient air humidity ( and forget all that notion of...well you dont' have a good enough humidor. Been through all of that ). If you're not intel with a climate controlled room, no little box is gonna protect your cigars from swings in temp/humidity. Ok. Got it ? Get that out of your head now. Not one you can afford. You and me, we're talking peaks and valleys and trying to keep in a range. No $35 or $80 or $200 humidor is going to prevent this. Trust me. I've had 10's of 'em. Now I use a locker at the local cigar shop for my best cigars and even then...they aren't intel. It's not like they are stored in a multi-million dollar clean room. My cigar shop is an old house on the north side of San Antonio.
And this is just one reason a cigar can unravel. Yeah, it can be rolled impropery but a cigar, ONE cigar...who cares. I buy boxes. Any cigar question of this nature is moot if you aren't buying by the box because, how would you know ? And that's not even going into which region or factory. Too many factors.
So, there's the tip of the iceberg on THAT question.