The synopsis is: we have the long-standing popularity of the name "Isabelle" and context that much of the English speaking world has been influenced by Christianity for centuries. It appears that "Isabelle" and "Jezebel" have a (at least a partial) common origin:
Isabella is a feminine given name, which is the Latinised form of Hebrew Elisheba (whence also Elizabeth) or the Latinised form of Jezebel (אִיזֶבֶל, ʾĪzével, ʾĪzeḇel).
With this in mind, it is noteworthy that the differences between the two names go beyond the God/Baal dimension. Etymologies concerning Isabelle not only use "God" in place of baal, but also sound more pleasant: "Oath to God", "God is plenty", ect. Compare this to the theonym of Jezebel which has negative-sounding sobriquets: "devotee of Baal", "vestal virgin of Baal", "concubine of Baal".
One could argue that "Baal" can also just mean lord in Hebrew. However, given how ubiquitous the story of Jezebel is, it would be hard to imagine how a Christian society would look past the literary connotation of Baal as in the Canaanite deity, of whom Jezebel was the infamous priestess.
Why were some theophoric names, like "Isabelle" tolerated as holdovers despite a transparent paper trail that traces the name to its Canaanite pantheon roots, while other Biblical names, such as "Judas" appear to have far less sympathy?
Note: Just academic interest into the matter, nothing personal against anyone named "Isabelle"!