Complex sentence: The Alemanni abandoned the Upper Rhine and left the Ripuarian Franks alone, and the absence of profit to Clovis, who allowed his ally to retain the territory, allowed him to have the help of Sigebert during the conquest of the French part of the Visigothic kingdom.
Split into simpler sentences: The Alemanni abandoned the Upper Rhine and left the Ripuarian Franks alone, Clovis, who profited only a little, and allowed his ally to retain the territory. Clovis later relied on Sigebert's assistance during the conquest of the French part of the Visigothic kingdom.