All these older groups have fanbases. They have loyal, hardcore fans they have gathered over the years who more often than not only listen to their faves.
It is common to chart long on Billboard albums charts. Example : BTS's MOTS7 released in Feb 2020 is still charting. Also these older groups release reissues almost every year so there's that.
Social 50 has been scrapped. It used to be one of the metrics but now it isn't since mostly kpop groups chart on that one and Billboard cannot have that.
oh, thanks for the explanations!
so this is not only based on sales numbers but also on how much people listen to it? (yes I have lieterally no idea about any of those charts)
But I still don't get it tbh, twice is third on bb200 and non existent on hot100, so how does it add up to rank 1 when the social stuff got scrapped?