Evolution and selling out is pretty much expected of any artist that goes mainstream (or they remain obscure forever). We know Metallica fans didn’t give a shit about the Black Album, Load, and Reload, but I think Metallica first sold out with Ride The Lightning. For Whom The Bell Tolls, Fade to Black, and Escape are more poppish and are nowhere near thrash metal. At some point the artist is going to change their sound, and when that happens, there will be controversy.
If changing your sound to something more commercial and poppish makes you a sellout, than you must admit that Genesis, Yes, Rush, and King Crimson (just listen to Heartbeat and Sleepless) all sold out in the 80s.