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The FX 9590 does have really high clocks, but being an older architecture it has lower performance for the clockspeed. It's not just about clocks, since a newer CPU will have more transistors (the majigs that do all the math), so it can get more done each clock.
However, if you want the best CPU for video Editing, consider AMD's newest, the Ryzen 7 3700X for $330, which competes in performance with the 9900K (beats it a lot of the time and in fact made tomshardware's best recommendation for a work CPU).
Or for the same price as the 9900K, you can bump up to the Ryzen 9 3900X, a CPU with 12 cores and way better workstation performance.
Hopefully this helped