The NFL gave Fox credibility. Married with Children was Fox’s first big hit. They were still the number 4 network before the NFL.
The NFL deal also prompted Fox to acquire a 20% stake New World, giving it VHF stations in twelve markets where they'd been with UHF affiliates. Eventually Fox bought all of it, making those stations O&Os. The improvement in signal and facilities was hugely important to Fox's growth from that point on, and it likely would not have happened without the NFL.
