For a short period of time in the early Middle Ages, Viking groups attacked and raided various settlements in the sparsely populated far far northwest corner of a backwater continent. Since monasteries and churches were some of the wealthiest and thus most appealing targets in their paths, occasionally they ransacked monasteries and churches. They frequently slaughtered the monks and nuns living in the religious houses or attached to the churches. They seem to have occasionally kidnapped monks as slaves. (The only reference I've seen to barbarians kidnapping specifically nuns is from Marseilles, not England). We hear about these particular attacks perhaps disproportionately, because the people making records of them in chronicles and letters were primarily monks and other clergy.

[It's clear from letters at the time] (https://www.reddit.com/r/AskHistorians/comments/3pcwan/did_the_vikings_pose_a_threat_to_the_christian/) that the Viking raids on churches and monasteries were believed to grievously threaten the morale of the surviving religious of a convent or church that fell under attack. The massacres seem to have caused specific monks to question their commitment to a religious life, since it appeared the saints had no interest in protecting them despite their devotions and prayers.

Meanwhile, Christianity was taking root on the European continent, and what scholars think was the era of mass conversions to Islam was just barely beginning. The Christian world stretched from Ireland to northern Spain to Ethiopia.

Did Vikings threaten the extent of religious zeal among a few monks and nuns? Sure. Did they threaten to wipe out Christianity? Absolutely not.

That has to be a no. There is simply nothing that indicates they even were interested in any way overthrowing Christianity. They indeed raided monasteries, but not for religious reasons - monasteries had accumulated wealth and were good for plunder.

Norse paganism itself was not a canonised religion - the vikings themselves were religiously diverse, and not interested in missionary work. I do not know of any sources of viking fighting religious wars of any kind. They were happy to trade wherever there was money to be made regardless of of religion.