Different crowd. The Eagles were the official band of middle class parents -- the house band at United Colors of Benetton. They waved the AM flag with Elton John and god knows who else -- Seals and Croft maybe? Dan Fogelberg? Jesus, what a horrid decade...
Zep, the Who, Pink Floyd and the Dead all had their bite of the apple, assuming the apple is only white people (which you could safely assume if you were talking about anything with national breadth). Even the Stones were diddling around in the top 40 of all places, although they were running on empty for half the decade. Oh, my god, I wish I hadn't thought of Jackson Browne. How did he miss being in the Eagles?
Anyway, Elvis probably outsold them all -- a sad lounge act who checked out about the time the ABA folded. Heck, the Beatles may have outsold them on sheer nostalgia.
Let's just say the 70s has the greatest inversion of talent to sales of any decade in history. No wonder they thought rock was dead.