Maybe he was concerned the stove and fuel would be stolen if left outside.
Not at all. This is one of those close knit "everyone knows everybody" communities. Fear of someone stealing equipment left outside the tent is not a factor. 
I cook inside tents, in particular when the weather is bad in the winter time. I am fully aware of the risks, and I do take what I consider adequate precautions. In fair weather I enjoy cooking outside. I think I share this attitude with lots of people who enjoy winter camping. Still, this is not something I recommend - it is all about personal responsibility and evaluating personal skills, risks and rewards. 
As stated above, the leaking of propane is a special risk that you need to take seriously. It turns out it was used a 11 kg (25 pound) bottle that was left in the cold pit of the large tent (a lavvu, which is the sami version of tipi). Most likely the coupling between the bottle and the stove was only half-way on, enabling propane to seep out through the night, filling the cold pit and also seeping out into all low lying areas nearby. Conditions was apparently just right for that propane to go WROFF and ignite the tent and anything flammable inside it. In my view, your regular gas canister has plenty enough fuel to replicate this particular accident, so don't think you're safe because you don't drag 11 kg bottles of propane with you on camping trips. 
But the lessons goes beyond propane. Even a trangia stove can cause havoc if you're clumsy - my pet scenario with those is filling a still burning stove (invisible flame), have the flames leap into the fuel bottle and then either have an explosion or spill burning fuel just about everywhere. White gas and paraffin stoves can produce really spectacular fire balls (so can a propane stove if you feed it liquid propane without knowing what you're dealing with). White gas fuel leaks are particular volatile. Wood stoves can throw sparks. Any stove can tip over. And so on and so forth. No matter the stove, synthetic sleeping bags and clothing ignite very easily, burn hot and melt into the skin.