Possible crown rot, what went wrong?

[Wiakor]

I have about four orchids, mostly phalaenopsis. My housemate has a few as well. I offered to help repot hers as I had done with a few of my older ones after they lost their flowers. Her larger one had some withered leaves and I suspected it was the substrate. The other orchid was smaller and healthy looking. The two lower leaves had yellowed and fallen off, but I assumed that was due to them being older leaves.

I repotted her orchids. The withered leaves one had some black spots on the roots, slightly rotted, but otherwise decent. The smaller one had glorious looking roots, in fact probably needed a pot upgrade. It was packed in completely in LFS moss. I repotted them both in medium size bark I had soaked, mixed with a small amount of fresh LFS moss and perlite. I informed her to not water them for a week to 10 days.

Well, today, two weeks after the repotting, the small one's whole body fell away from the root system. It still had green leaves, nothing saying it was sick, just today it fell off and looks like it was rotting. I'm devastated. How did this happen? Was it me? Was it leftover affects from being in LFS? It felt strong during the repotting. Can it be saved? Will more leaves grow from the roots despite the leaves and a part of the body falling away?

I'm hoping to understand what happened before I have to explain I may have killed her plant.