I fail to see how the article answers the question in headline. It seems to say "because we all became nice Social Democrats with strong suport" but doesn't really answer the how.
Also, the references to Black Lives movement seem very out of place. BLM activists appear quite confrontational and in many ways the exact antithesis of how Norway, Sweden, Finland and Denmark became what they are.
In a word, being divisive (e.g. by bashing Donald Trump a lot, however well deserved) isn't going to reach out and win over anyone who disagrees with you.