What are some of the typical reasons why empires and dynasties tend to decline and fall

There are many reasons for the fall and decline of empires and dynasties. Some empires were declined because of army conquest from neighbouring empire, weak military and administration also natural calamity like volcano eruption, drought which head towards in the decline of empires.

Dynasties tend to decline because of no heir to rule after his father succession. Weak ruler, who make wrong policies that led to the decline of his kingdom. Fights among the brothers for the power to rule led to greed and corruption, which results in doom.

the british army and british colonist were by iroquois indians.

in all honesty, it really hasn't. except that hitler killed himself.