Yes, many times. Historically, it seems like the very strong empires first defeated themselves and once they were sufficiently weakened for outside forces to be able to threaten them ... they still kept being self sabotaged by their own elite who prioritized maneuvering against each other for temporary power/wealth grabs over working together to face the outside threats.

The late Roman empire has a bunch of good examples: blatant corruption, over taxation of the poor, many assassinations, sabotaging their peers that were trying to improve the situation, constant civil war, the battle that destroyed the military backbone of the western Roman empire was fought between romans, ... And all that while the empire was being torn apart by outside invasions.

Or a more recent example: the polish Lithuanian commonwealth had a paralyzed government thanks to corrupt elites with veto powers in their parliament of nobles (sejm) and only once the nation was mostly destroyed and the nation on the cusp of final destruction, did the sejm introduce some sensible new laws, but it was too late.

With smaller regional powers you can have cases like "they were in a golden age and had never been as powerful, but then the mongols appeared", but with hegemon empires the failure of their inner workings is always going to be instrumental in their own demise.