Why was Ghanaian highlife so popular amongst Easterners in the 70s and 80s? Why did bands like Peacocks International sing several songs in Twi and other Ghanaian languages? Why were Ghanaian highlife musicians so popular in the East that for a while they took up residence in cities like Aba, Asaba and Onitsha?

I don't know what it is, but I personally can't resist classic Ghanaian highlife.

maybe the Maestros failed to mentor protegees and pass on the art. many Trained musicians are known to be selfish.
Also, maybe the art has a high-barrier entry. In addition to be talented, you must at least play one instrument. How many musicians of nowadays can whistle, talk-less of play an instrument. The very few that do, like don jazzy, flavour, etc are very unique in their output.
Thirdly, "tempora mutantur et nos mutamur in illis" (the times change, and we change along with it). So maybe, the times have changed.
I'm avid collector, connoisseur, aficionado nay cognoscenti of highlife music.