This sentence on the Yahoo! front page includes a grammatical gaffe. This is one of hundreds of Yahoo! sentences where the verb doesn’t agree with the subject, but the rest of the errors aren’t as easy to spot.
Some nouns that are singular in form, like rest, may have a plural meaning and take a plural verb. In this case, rest refers to more than one fast food chain, so its meaning is plural and the correct verb is aren‘t, not isn’t.