Gruden got a good dose of his teams talent level by the time training camp ended.
Clearly he must have realized his 2018 roster was maybe 2 or 3 years away from being where his long term vision and goal is.
If I was Gruden and believed the Raiders roster was not going to be a legitimate consistent playoff contender, I would've traded Mack for what they got in return.
If the Raiders end up blowing it on the 1st round picks they got in return, he will obviously be ridiculed for this decision.
Mack is an elite player but the Raiders are moving to Las Vegas in 2 years and Gruden wants to build his roster the way he visions it.
Gruden is not under the pressure of we need to win now...
Obviously Mack was not the piece of the puzzle he felt would put his team over the top. I have no issues with his strategy sending Mack packing for 2 first round picks.
If what you have doesn't fit your vision...