What is one reason the guptas lost power

The Guptas lost power because of a couple of reasons. They lost a substantial amount of territory and a lot of imperial authority caused by their own erstwhile feudatories and the invasion of the Huna peoples from Central Asia. A minor line of the Gupta clan continued to rule Maghda after the disintegration of the empire, but they were soon ousted by a Vardhana ruler who himself established an empire in the first half of the 7th century.