Upvote:33
Colin McEvedy argued in his Penguin Atlas of Medieval History that conversion was a good political move for the Franks.
The thing you have to realize about France is that even though it was essentially conquered by the Franks (Germans), they were never much more than a ruling class. The common people continued to speak Latin, which over the millennium slowly became the language we today call French. We can assume they would have been inclined to keep other aspects of their culture too, and that includes their religious beliefs.
At this time most of the larger German tribes had converted too, but they generally would convert to the heretical version called Arianism*. This conveniently allowed them to call themselves Christian, but without acknowledging the authority of the Pope. Colin's argument was that by converting to the standard version of the faith, the Franks were able to better appeal to their subjects, the common people of France, as their protectors. This would have strengthened their grassroots political support.
* - No this has nothing to do with Nazi "Aryiansim". It was a minor difference over the mechanics of the Trinity, which ended up being far more important politically than theologically.