I absolutely agree, but those two collapse examples are extremely complicated. Historians generally conclude the collapse is due to political instability, barbarian invasions, disruptions to international trade, in-fighting, collapse of agriculture (likely due to climate change) and various other factors.

All of these various competing problems can be summarized into three categories: economic, defense, and political. By far the least critical of those three is defense. I am saying this as a military office who has studied history. If you are wealthy you can fund a better military and better defensive protections. If you are poor but you are politically united and guided by strong leadership you will still probably figure it out. If your economy or food supply fall apart you likely won't have the political unity necessary to mount a strong defense. Likewise if the people are disenfranchised or selfishly entitled there will be less political will to prop up the economy.