Why was the hiring of germanic mercenaries by western roman emperors a mistake?

The hiring of Germanic mercenaries by Western Roman Emperors was a mistake because it undermined the loyalty and effectiveness of the Roman military, as these mercenaries often had divided loyalties and could not be fully trusted. Additionally, their presence contributed to the erosion of traditional Roman military discipline and cohesion. This reliance on foreign troops weakened the empire's ability to defend itself and ultimately facilitated the rise of internal strife and external invasions, hastening the decline of the Western Roman Empire.