The aluminum wire connections
are the issue, not the fact that the wire is made of aluminum.
In the mobile home manufacturing industry especially, the wiring methods of aluminum branch devices were employed that was not properly done. Add to that the fire spread rate at which any small or other size fire started would end in a total loss.
Mobile home were made with the cheapest electrical devices available...maybe even built only for mobile mfg and the installation always performed at a very quick pace so no attention was paid to details. Yes, copper would of been hands down
the better choice in mobile homes, but $$$ economics
$$$ got in the way.
The cheap push-in spring loaded wire terminations on switches and outlets were not suited for soft #10 aluminum, that, together with circuit count quantities not being more than minimum to pass code and those circuits often being overloaded and never as forgiving as the more $$$ COSTLY $$$ copper wiring. Using a no-oxide paste between wire and mating surfaces along with the wire wrapped clockwise forming an eye around the compression screw of the switch and plug devices with proper torque applied for maintaining great tension is what needs attended to to have a proper tightened non-heating connection. Slightly loose connections makes heat...heat makes even looser connections making even more heat...which makes even more , more loose connections which makes even more, more heat...which...see where this is headed???
Now days only larger multi strand aluminum wire is available for use (but not for home building) and only mechanical tightened or indent compression are acceptable methods, and both require no-oxide paste be used.
If today an aluminum wiring job has lasted for several decades already in a stick built
(1966) house it must of been built right when installed or was brought up to standards previously, or it would have never lasted this long. The hazards seen in mobile homes did not wait decades to show up in those occupied mobile homes.
Not saying to not use due caution in evaluating the house's wiring, just saying all/any aluminum is not a total impossibility.
My short answer on aluminum wire is..."It is only as good as the hands that do the connecting/splicing."
Sorta like computers, S#it in equals S#it out.
Best to use copper if you don't know what's different between the two.