they don't sell. how many V6 Challengers do you see?
lets look at classics, how many people want a Challenger with a slant 6, a Camaro with a Chevy 250 cu in inline 6, or a Mustang with a Ford 200 or 250 cu in inline six? No one they all want a 340 383, 440, or 426 if Mopar, 302, 327, 350, 396 or 454 if GM or 289, 302, 351, 428 if Ford. That's just how muscle car enthusiasts are. They really don't care what is the latest thing being pushed by regulators. And why, they are going to walk away from an electric Charger or Challenger.
for most Americans who know what a Challenger is, high performance is spelled V8, it has not or ever been V6. A few younger people might want a turbo V6 but they won't be the majority.
Keep in mind the Challenger, Camaro and Mustang are legacy models that sell to a certain group of a certain age, or who had parents who had the originals.
And, most people who want a Challenger know full well the disadvantages of having 700 hp V8. That is exactly why the 5.7 and 6.4s sell well, they have the muscle car feel without the drawbacks/expense of the Hellcat.
So if Stellantis is foolish enough to walk away from an established market, so be it. They already did this to the company who invented the mini van in North America, that alone proves their poor judgement. It seems that Honda, Toyota, etc don't have too much trouble selling vans.