What causes scale rot?

I have researched it alil bit but I have seen alot of post on here regarding the issue. Is it a lack of of care for the owner? just curious because I have seen some pretty extreme cases on here and other forums.

It can be caused by many things, but I think the most common is being on bedding that is too wet. Or, the conditions of the enclosure is too wet.

Filthy conditions and/or damp substrate can cause scale rot.

So pretty much not keeping up to date conditions with the tub or tank.

ok this might be a bump question, but here it is how long do they have to sit in that to get that way. It has to take months and months to get it right?