BTS history is the exact contrary of what you are saying. Korean people slandered them an multiple occasions and did not like them a lot when they were "nugu" in Korea until the beginning of 2017. They were still called nugus at this point even if they were pretty successful but in fact they were only breaking records internationally especially in the US. By the end of 2017 and the beginning of 2018, their international achievements became hard to ignore so they gained more exposure in Korea which brings them a bigger fanbase and more casual fans/listeners.
They released Dynamite in August 2020 then BE a Korean album with a Korean title track, Life Goes On in November 2020 and this year they came back with their usual yearly Japanese albums and then two English singles that were presented as a trilogy with Dynamite so now they will likely come back with a Korean album. It 's not like they had no intention at all to promote Korean songs in Korea ever again. Between 2020 and 2021, all the members released at least a Korean solo song.
I understand your point too though.