Tourism is the largest industry in the state of Florida. If that sweetheart deal helps to bring in tourism dollars, it stands to reason that the influx of tourism dollars will suffer if that sweetheart deal goes away.
Disney World's Orlando theme parks bring in, rough, $19.7 million a day. That's not all going into Disney's pockets, though. Much of it goes to pay the 77,000 people employed by Disney in the Orlando area (it's the largest single-site employer in the country). If those people take a hit, then the merchants where those 77,000 employees spend their money will be hit, as well. With fewer people vacationing here, area restaurants and hotels will suffer. Their employees will see layoffs, and will no longer have as much money to spend with area merchants.
This isn't something that could hurt only Disney. If Disney suffers a big financial hit over this, the entire Orlando area will suffer.
I think DeSantis was so focused on hurting Disney that he may not have fully considered how badly it could hurt those who have no connection to Disney...
Of course, the glaring irony in your comment is that it's a conservative government which is doing the taking...