"...the maker of the best air fryer now has to bid on ads as well, if only to protect the sales they were entitled to in the first place." No company is "entitled" to any sales.
The point is that, because of their product’s merits, they would organically be the top ranked search result. But due to advertising, they have lost that spot and now either must give up sales or also advertise.
1. qualified for by right according to law
2. having a right to certain benefits or privileges
3. having a right or legitimate claim to something
No company is qualified for sales according to law, or has a right to sales, or has a legitimate claim on sales. Sales must be earned by besting the competition.
No company is "entitled" to any sales.