this isn't terrible, bit it's far too trusting of the sources, which are what they are: mostly written by clergy. it just takes things at face value. which, on some level is necessary, because it's what exists. but, on some level is terrible, because anything ever written by the clergy during any period should be taken with a grain of salt. these people were professional propagandists that were given the task of recording history in a way that is favourable to the church. we might call it orwellian, if it weren't for the fact that orwell wasn't making anything up - he was just interpreting papal society.

there's a broad amount of recent scholarship that is slowly coming to the consensus that the vikings were unleashed by charlemagne's genocide in saxony. this is the reason they targeted churches; it was out of fear of being the next target. it may also be the reason they were so successful. they may have had some local support, in the form of lingering odinism in france and england. it's known that there were periodic "reversions" for centuries, always blamed entirely on the norse and never on the locals.

at this point, we can't say anything with certainty other than that the sources are christian and therefore not trustworthy and consequently need to be revised. but, the broad narrative you're getting here is likely a total whitewash.

https://www.youtube.com/watch?v=R7SX3ulV_tk

i'd recommend that some of these structures be carbon-tested to verify the clergy's claims as to when they were built.