Red Five is correct. H-46s were dropping like flies - multiple engine failures (think you needed 3 x IOT become a HAC) and maintenance requirements were thru the roof. This was also a part of the post-Desert Storm RIF.
The history according to me -- Originally, there wasn't that much thought to be spending time in the dirt. Of the 8 x 60S going to CVW squadrons - only 5 x would have the kits to make them a true block 3 (and those would likely be swapped - 52 kits total if my memory serves me correctly). This was not too far off from an old HS squadron - 2-3 x HH60Hs and about 5 x crews. Those crews focused on CSAR, due to the requirement to handle CSAR for independent CSG ops. In 2001, it took 2 x squadrons to handle the CSAR requirements in the opening days of OEF. SOF ops, pre-9/11 were pretty rare - mainly HVBSS for Iraq Oil Embargo stuff and when SEALs actually deployed on ships. The CSAR crews were the ones doing the SOF stuff. The old syllabus had ~ 6 total NSW cards, 12 x CSAR cards to Level 3 - so you can see the focus.
As OEF/OIF went much longer than planned - The number of block 3 kits for the 60S increased to a buy of 200+ kits. At the same time, a group (of an HS background and jealous of the HCS-4/5 deployment), used less than gentle methods to make Expeditionary and CVW one and the same, tactically in hopes of building a larger tactically community that would be used by the larger Joint enterprise. OSD had initiated a number of 'how to fix the rotary wing shortfall across the Joint Force' studies - and there was possibly (my supposition) a thought that HSC could save the day. That group saw the NAAD detachment as the first of a series of wins.
An emphasis on CAS started ~ late 2000s when CAS was a huge focus for our fixed wing brothers - IMHO, then NSAWC and/or SEAWOLF thought that CAS should be in their bailiwick, so they began an emphasis on CAS. The 'why' has always bothered me on this - as HS had never been tasked to do CAS. In essence, a decision had been made to grow the mission set - without a 'likely payoff' to community utilization of the capability. I never liked it being jammed down my throat - my thought - I am lift for the team and have only enough firepower to defend myself / cover the team IOT give other platforms time to set geometry for an attack. Note - this was well before the M197/rocket system came online and the FAC/FIAC craziness.
Add these together with a shotgun marriage of CSAR/NSW HS mentality with the HC log/SAR mentality and a lack of performance of the minesweeping systems/LCS- and you get what has been discussed on the previous 46 pages of this thread (amongst another multitudes of threads here)..
This may be the Howard Zinn version of HS and HC becoming HSC. Feel free to talk amongst yourselves.