That is the way it's always been---then and now too. People prefer to give their time and energy and voice to what genera they are into. Either that, or curl up with a good book.
In many places, if a bluegrass show was going on in town, and a blues show was somewhere else in town, each had their own audience.
If those two shows were on different days, the same bluegrassers would still by at the bluegrass show for the most part. And the same blues people would be attending the blues concert.
If all those people had gone to both concerts, each would've done better at the door.
Dylan is correct. But, also, he is BOB DYLAN and all that that entails. He can jump ship from one style to another just because he wants to do it---=-and because his people will follow him anywhere he goes after he's blown in their ear! ("Blow in my ear, and I'll follow you anywhere!"----Henrik Ibsen -- a.k.a. Henry Gibson)
If it feels good, we'll do it. If not, we won't.---the old Pleasure Principle