Hygiene is usually pointed out as one of the reasons but I’ve seen that the idea of medieval europeans being unhygienic has mostly been debunked. Also they knew well enough that they had to isolate themselves from the sick and burn the bodies.
On top of that Asia had some major cities 10 times bigger than London such as Sarai which had a great influx of people from all around central Asia if not from all Eurasia and didn’t seem to have been hugely affected by it.
So am i missing something?
I can only speak to one part of your question: North Africa was actually hit extremely hard by the Black Death and did not recover until modern times. For example: Egypt, which historically was one of the largest regions of the Mediterranean World, experienced such sharp declines that it took until 1800 to reach the same population as under Rome in the first century, which was about half the population of the island of Great Britain (5 million vs. 10 million). (1) Egypt lost perhaps 1/3rd of its population in just 18 months. (2) There would then be 27 additional waves of plagues over the next 160 years (3), costing the central state 80% of its tax revenue (the closest thing we have to census records for the 1500s). But the effects weren’t limited to Egypt, which actually “survive[d] the Black Death better than the rest of North Africa and the Middle East”. (2)*
John Iliffe is actually an Africa specialist, and posits Sub-Saharan West Africa “was protected by the Sahara against Old World epidemics”, finding that only in the 1740s were the regions plagues even remotely in-sync with north of the desert (indicating closer integration). (4)
*Quote: “Algeria suffered five plague epidemics during the eighteenth century alone; Egypt and Tunisia, three. Contemporary mortality figures are unreliable, but the epidemic of 1784–5 was said to have killed one of every three or six people in Tunisia. “ (168)
1: p. 160, Africans: The History of A Continent, by John Iliffe 2: p. 66, Iliffe 3: ch. 14, The Fortunes of Africa by Martin Meredith 4: p. 68, Iliffe
There are two excellent and semi-related answers already out there, both from /u/mikedash (not to discourage any additional contributions, of course).
First one is more related to your question regarding Asia. This one is unfortunately not in the FAQ, although I'm sure it's just an oversight.
The TLDR of that one is... the black death may not have originated in East Asia at all!
Secondly, and as a partial aside, I've attached what I consider to be one of the most exceptional answers ever produced in this subreddit's history. This is on the issue of Poland during the Black Death. https://old.reddit.com/r/AskHistorians/comments/79dwua/why_did_poland_have_lower_rates_of_black_death/