Hammerstone had some WWE tryouts, the last of them being in 2017, when the Fed was on a hiring spree. Based on what he told on this interview, they just were too full and the whole hiring process was ass. While his experience there wasn't good, he did turn his career around and is fucking DOPE.
As for Fatu, both AEW and WWE got in touch, but according to him, they were "too late".
I imagine that right now, it's a matter of time, just waiting until their contracts are expiring so that the bigger boys can make moves.