“I doubt Trump is really that big of a draw.”
That’s just willfully ignoring reality. Look at the debate ratings pre-Trump vs. Trump. Why do you think people were tuning in? Jeb!?
Why were Republican primary voters tuning in? Eight years of Obama.
Why were Democrats tuning in? To watch the side-show that is Trump.
So yea, they'll lose two sets of viewers, the in the tank Tramp voters and the Democrat gawkers. Will Fox not make as much money? Probably they won't.
Now more importantly, do I care about Fox losing money? No, I don't own stock in Fox.
Your presumption is that if Fox loses Trump wins. That is a false conclusion. Trump doesn't make a lot of bad PR moves, but this was one. All undecided voters will continue to tune in and Cruz is going to shine like a new penny with even more time to do what he does best.
Yes, Trump has a personal feud with Megan Kelly and they both look the worse for it. Given that Trump starts a new personal feud every week, there is no reason to pay much attention to this one.