That’s what makes no sense he was getting stellar rating but no ad revenue? Those two things don’t go together. It’s an either or thing, not both.
Time slot? Good ratings at 8 PM or 9 PM are a lot more profitable than good ratings at 5 PM.
Those boycotts worked. Big name advertisers didn't want to associate with his program, so Fox had to settle for some of the ones that have already been mentioned - PetMeds, Goldline et. al.
There's a reasonable, even likely chance that whomever replaces Beck will double (or more) the ad revenue, even though they may not reach the same level of ratings.
Of course, Beck has been getting almost the exact same number of viewers as Bret Baier and Shephard Smith's 7pm show. I think his replacement will probably do the same without the advertiser problems.