North Korea ending up a monarchy was mainly because Kim Jong Sung didn't like that the USSR and China had ended up liberalising after the deaths of Stalin and Mao and wanted someone he could trust to succeed him.
The difficulty with Timeline L bringing anything back is that the last we heard they didn't even have the concept of parallel universes. Going from there to interdimensional travel in five years seems like a heck of a leap.
Britain might have sent troops if Hugh Gaitskell had lived or if the Conservatives had won the 1964 election. The Americans were willing to offer a lot of economic assistance in return but Wilson refused, in large part because he knew the war would be unpopular.
Diversitarianism's insistence that everyone is entitled to their own truth seems like it would cause serious problems with formulating a response to climate change (or a global pandemic, for that matter).