Ex-philologist and historical linguist here, and I don't find the heuristics all the improbable. Change in the field is largely generation--the old guard dies and the young turks rise to take their place. Peer review filters out the noise, but is also reactionary, and informed by taste.
Historically, German, French and Latin have all been high-prestige languages, and scholars have focused on their relationship to English. There's been plenty of relation to find, no doubt! No one argues for direct lineage w/ Latin, but German roots have always been plausible and palatable.
Norse, though? Some would have found that scandalous. Borrowings--sure, ok. "Influence", of course. But lineage? No, certainly not.
Doesn't Middle English differ enough from both lineages that it could have been a creol of old norse and old english, that then later developed into a language proper?
Historically, German, French and Latin have all been high-prestige languages, and scholars have focused on their relationship to English. There's been plenty of relation to find, no doubt! No one argues for direct lineage w/ Latin, but German roots have always been plausible and palatable.
Norse, though? Some would have found that scandalous. Borrowings--sure, ok. "Influence", of course. But lineage? No, certainly not.