Why were the franks able to rule gaul/france

The Vandals launched a massive invasion of Gaul in 406, and in the ensuing decades the Franks took advantage of the overstrained Roman defenses. ... He then took advantage of the disintegration of the Roman Empire and led the united Franks in a series of campaigns that brought all of northern Gaul under his rule by 494.

Explanation:

b. 155 enlisted men and no officers

well this is going to be a long answer lol ok so the visigoths were a branch of the goths who frequently raided rome, uh the hunas attacked the guptas a lot and weakened them, uuhm of course the romans used math and science in there every day lives i mean they had a whole empire to run, and rome was split into east and west by a general named diocletian. hope this you! : )