You can check the status for the firefox package in Fedora at https://admin.fedoraproject.org/updates/ which shows firefox-72.0.1-1.fc30 as "testing" (that is, you can install through "yum --enablerepo=updates-testing update firefox"). The reason for it not being promoted to stable yet is, according to that page, "disabling automatic push to stable due to negative karma" - that is, the update was marked as broken by a couple of people.