What were the causes of decline of loyalty and discipline in military that led to the fall of roman empire?

Answer 1

The fall of the western part of the Roman Empire was precipitated by the invasions of this part of the empire by the Germanic peoples, rather than citizens indifference and loss of patriotism. It was said that many citizens were indifferent to these invasions because they were not worse than the Roman government. This attitude was due to resentment towards the oppressive taxation regime which the Roman state needed to fund a large army and a bloated bureaucracy.

Answer 2

As the Gothic people move into the Empire, they were used first to settle on the border to protect against later arrivals. then later recruited into the army. This army progressively changed ethos, and its commanders gained increasing influence. Finally, the commander or the Roman army became a Goth, Odoacer, who took over the emperorship form Romulus in 476 CE.