Glory of the Great Dead

Why was Cnut so great and how did a Norman Duke get the idea to invade England?
I have spent six years studying, reading and trying to understand what made Cnut the Great so great and what led to the Norman Conquest of England in 1066.
Information from the so-called dark period is extremely scarce, limited to a few accounts written by contemporary monks and some much later documentation by people like Snorre and Saxo, as Norse, the language spoken in the Viking age did not include writing,
By studying most of the books written on the subject, and by extensive exploration of what engaged people have written on Wikipedia, comparing differences between sources, and using the logic of the Viking traditions, I believe I am as close as can to the true story.
I have also being inspired by books like Queen Emma and the Vikings by Harriet O’Brien, Queen Emma & Queen Edith by Pauline Stafford, Emma the twice-crowned Queen by Isabella Strachan, The Empire of Cnut the Great by Timothy Bolton, History of the Normans by Dudo of St. Quentin and of course Encomium Emmae Reginae.
However, as we have no real scientific proof on which to rely, I have chosen the form of ‘faction’, a story