I'm sorry about your loss. This has happened to me many times and shippers almost always fall back on "packed incorrectly..."
But IMO shippers are also almost always right. Most folks who buy and sell used audio have no idea of how delicate audio items should be packed for shipping. I can't tell you how many turntables I have purchased that were bagged and set into a box full of packing peanuts. Needless to say, I almost always ended up pouring the broken bits of turntable out of the box.
My suggestions are:
1. Hard foam and strofoam packing is a big no no. As is soft foam. Blur or green polyethylene foam works well, if you know how to use it. I typically assemble a "cradle" made of fabricated pieces and assembled with a hot glue gun.
2. You need a strong, NEW box. Don't reuse or recycle another box. Most old boxes are soft. Order a new box from Uline or one of the shipping goods firms. I try to use 2x wall thickness but 1.5x will work for lighter pieces. This will also negate the need for double boxing. I only do that for very high priced items going internationally.
3. You need a minimum of 2" of clearance between the box and your equipment - 3" is better. That means that your foam cradle is keeping your item that far away from the box boundaries. But the cradle needs to fit tightly - absolutely no slack or slop when the box is closed.
4. Tape your box well. That means using good quality tape and knowing how to use it. Life is too short for cheap packing tape. and more tape is not necessarily better if the tape is of good quality.
Have fun
