As sorry as I am and as tragic as it is that you lost an hour of your work, it also seems to be true that you did not inform yourself in advance about the related topics in order to be informed and prepared in case of the situation you faced.
But okay, so you want to know why something isn’t working the way you imagined it would work in your favor, in case what just happened to you happened?
Here I recommend that you familiarize yourself with the functionality and topics explained in detail in the Krita manual: Saving, Backup, Auto-Backup, Crash Recovery. You can find it here:
Alternatively, you could use the forum search to find the countless topics on auto backup and, for example, apply the damage minimization options I suggest there. For instance:
There is also a plugin that modifies the auto backup function available in Krita, which is exactly explained in the manual (and so often misinterpreted), to work in the way you imagined before the recent incident: