Compression Fitting Popped Off, What Did I Do Wrong?

So I slipped the nut on, then the ferrule and pushed them back on the copper pipe, then I put the compression fitting (cutoff) on the pipe until it bottomed out, then I pushed the nut and ferrule towards to compression fitting and threaded it by hand, then I used two crescent wrenches to tighten the fitting.

I did five fittings this way and one of them came off. I double checked the tightness on all of them and they were all very tight.

The only other things going on is that the city recently replaced the meter and at seemingly the same time the main cutoff started to leak when fully closed and this fitting came off at that time or sometime after. It wasn't leaking much, but it was a steady stream when I looked at it. The water wasn't used for a couple of weeks while the main was leaking and at some point my compression fitting came off and caused a leak in the house. I can't imagine pressure would build up enough to cause something like this to happen under really any circumstance.

There was also some foundation work in the house but I can't imagine the pipe in the wall was moved with enough force to make the cutoff come off. There was some damage to the hole where the copper pipe came in, but even still it seems it would take a lot of force to make the fitting come off, maybe even enough to totally break through the drywall, and the drywall would be the part to fail, not the fitting.

What did I do wrong here?

It's hard to say.
You need to snug a compression fitting pretty good.

I put some muscle into them when I'm installing.

When you took apart the leaker, where was the ferrule....was it back a 1/4" or so from the end of pipe, or had it accidentally slipped up to the nose?

If it slipped off it was either not tight, or the tubing was damaged so it was undersized. The pressure would have to have been "enormous" to push a properly installed compression fitting apart, and by that time it would have caused other problems.