My thoughts are that on the offense, the Cardinals have two young building blocks that could be elite players at their position in Murray and Humphries. They brought in a seasoned All Pro in Hopkins. The overall talent on offense would make this a good offense even with replacement level coaching.
The defense needed a star player. Baker was on his way, but Jones will be declining and the Cardinals desperately needed a versatile second level defender much more so than another WR.
By draft day, I wanted OL first. Wills or Becton. Wirfs was a consideration too, but the first two are a bit more talented as pass blockers.
But Simmons was arguably the best player on the board and he fit a massive need. Early in the season Campbell made it look like the pick of Simmons was superfluous, but Campbell really fell off a cliff and Simmons has started to show his potential, which is a guy who can make plays in all defensive phases, not just a rusher, cover backer, or run stopper.
My faith in Simmons is now to the point that I expect that he is going to be a top ten LB next year. He is around the ball too much and is too talented for him to not meet those expectations.