The parties involved can always petition the Supreme Court. They're free to take up any case even if there isn't a split between lower courts.

Because it conflicts with the holding in another circuit, called a "circuit split," which is one of the most common causes of the Supreme Court choosing to hear a case. The Supreme Court doesn't want forum shopping.

> In this scenario the precedent has already been set in the 5th, why would the Supreme Court hear it again?

A circuit split on an issue is one of the factors that traditionally weighs in favor of the Supreme Court hearing it, in the interests of uniformity of the law.

If the Supreme Court likes the 5th Circuit rule, they take the case it make it the rule, period.