'Twas probably part of the great UOR tidal wave and therefore not in any business plan past or present.
It is a fine example of blue suits flying planes that primarily serve the purposes of brown jobs and the resultant in-fighting over who is boss and who should drive between the two leading to the loss of the capability.
Nice one!
As far as I am aware, Sentinel and its associated ground stations were not part of any UOR, but a fully funded joint RAF/Army procurement programme.
Unfortunately it suffered from setbacks in the development phase and was late into service. Now that is in service I have no experience of any inter service rivalry over who owns the platform or product. 5 (Army Co-operation) Squadron is a fine example of RAF/Army jointery and seems to be doing a fine job in theatre.
I think you will find that the demise of Sentinel was probably a Treasury driven decision and had nothing to do with the military.