They would lose a lot of the sponsors or at best keep them for waaay less money, because they will not keep paying the club the same when they don't get the same level of exposition than being on the top league. Also can't charge the same for tickets or seasonal passes. Also the rewards for the league are way lower. Merch also would get cheaper. Much of the club income would get highly impacted, and will lead to lower contracts for players and general staff