The only question is what the hell took so long?
DeMarco Murray had a great year and needed to fade in year two. He was a top three RB and it's not wrong for a rookie to sit behind a top three back.
Midway through the year, Henry (as a sub) surpassed Murray in rushing yards and at that point he should have been given the keys.
Dion Lewis was a good free agent by 30 teams in the NFL. By former Patriots Jon Robinson and Mike Vrabel, he was a stud free agent big add. He was a key player and did do well in New England, they just never took the time to look at other perspectives.
Jalston Fowler was an excellent fullback, he was the top rated FB by PFF and could even line up in the slot in a pinch. The Titans curiously cut him and with FBs being fazed out, few teams were interested despite him being the best, until the Seahawks picked him up. He was Henry's college roommate, BFF, and lead blocker.
Between adding Lewis and losing his BFF, Henry did not run that strong at the start of last season. Eddie George met with him and pointed out several things that he clearly did different/worse. The Titans scooped Fowler up when the Hawks cut him. He smashed people in practice and even got a fine for doing so in a non-contact one. They had their bye and it was 2-3 weeks of Fowler but yet he didn't play in a game. All that hitting though, it juiced up the line and Henry and set everything straight again.
Henry occasionally shares pics of he and Fowler and they're still best buds. Fowler is still ripped in the pics. The Titans added a FB to the mix when Tannehill took over- usually Jonnu sometimes Blasingame, and Henry finished the season with 70ish percent runs from the I formation. While unlikely, I wouldn't be surprised if Fowler is in camp next summer as the FB has been a big part of their turnaround and there's no doubt he's still in super shape. Blasingame is a college RB that's learning the FB role. He's a fine blocker but doesn't have that reckless smashing mindset that FBs have. He might be Henry's backup next year.
Anyway, ramble, there were reasons and they kind of make sense even if I disagree and would have done things differently.