I think Stake.com would have included a clause in the contract, that if Everton gets relegated out of the league, then the contract between them gets terminated. It is obvious that you cannot pay a team, if they do not qualify to participate in an tournament, where you want to advertise your company.
It is a pitty that Stake.com are only sponsoring the lower ranked teams in the championship, but I guess having them sponsoring two teams in the lower ranking, gives them more exposure.. than sponsoring one higher ranked team.

Also.... the Drake stream took a lot of money out of their pockets... and that might be why we will not see a pre-monthly.
I think it's quite alright considering those are getting viewership as well, they can't just do sponsorships on Manchester united or city or Liverpool etc etc, those are huge amounts and they will not be able to get it. There are way too many clubs who do not like gambling sponsorships neither because they feel like it's too risky, it could get banned any moment and that is why they prefer lesser money most of the time and get other stuff. I think it would be wise to continue down this road as long as FA allows them to do so.
It's not that easy because betting and sportsbooks are always getting extra audit by these organizations and even if a single thing is missing, they do end up not allowing them to sponsor anyone. So doing it is really valuable without a doubt.