Froome has been linked to a move to ISN for a long time. The latter are in the position Sky were in ~10 years ago: they're new money and they're buying up riders.
Thomas isn't as good as Bernal and he wasn't as good as Froome pre-crash. He also has the same age problem as Froome: even if he were as good as Bernal (which he isn't), Ineos would bet on the rider that can deliver wins for the next several years rather than the one that still soon be retired.
Remember Wiggins being forced out by Froome? Welcome to the same drama, seven years down the line.