I'd say that, generally, imperialist motivation is a matter of gaining power. In a capitalist system, capital is power, so they are seeking capital.

The way I explained it was meant to break it down into a modern context to help answer the question, not to address imperialism in the context of feudalism or other systems. End of the day, someone is exploiting someone else for their own gain. It was just a matter of the context of the question and I erred on the side of keeping the scope within capitalism.

None of them were fascist. Fascism is specific phase of development of capitalist system, as MeowZedong explained, it is not just when someone do conquests and/or kills many people.

Although the mechanism isn't entirely dissimilar, all those you listed belonged to pre-capitalist levels of development (Napoleonic France was in progress of change but quite early) and are the effect of their societies reaching the boiling point of internal development saturation when it was ready for expansion, and also all of them followed earlier successes.

For comparison you might also add one of the most characteristical examples of Spain launching its global scale colonisation and conquests immediately after finishing centuries long reconquista.

Also note that neither of those cannibalised itself like fascism did, because they weren't capitalist. They just ran out of the force driving them and either collapsed or stabilised on some level.