They've decided, after an investigation by two firms, that they have ample reason to fire Les Moonves for cause, and
will not offer him a single penny in severance. Moonves will undoubtedly sue, but if they stand their ground, it could be a big step in the realm of corporate (and individual) accountability.
I would not be so sure that Moonves will sue. For one thing, CBS likely would have significant counterclaims against Moonves--and not just for the cost of sexual harassment claims against CBS arising from his arousals.
Heck, it's not out of the realm of possibilities that this was all worked-out with Moonves' attorneys, as in we will agree not to sue you if you agree not to sue us.
Also, this is not necessarily unique (other than perhaps the amount of money at stake). For example, Matt Lauer was shown the door without receiving any of the money owed to him under his contract with NBC.