I know there is no way around you but still .. By waiving him they offered him to 31 other teams, many of them already rebuilding so they have less problems with extra roster spot if they see future value (many eliminated teams putting lots of players on IR to make room). He may clear waivers or be claimed with equal possibility at the moment.
In any case the fact is that with releasing him they took the risk of losing a young DT player that looked like he fits their scheme & locker room, that they invested a whole year of coaching etc., were very happy with his progress and very happy with what he showed on the field after VV was injured to offer them a seamless rotation.
On the other hand they obviously liked what they saw in Kilgo so that might be the reason why they took a risk with Hamilton. Seeing Kilgo clearing waivers (having much more experience on the field on top D) maybe encouraged them to go with Hamilton instead of somebody else (Foster and Waddle were less active f.e., Coleman doesn't seem to be part of CB rotation anymore or the future, Richards looks completely expendable - and could go to IR w no risk etc.).
I do believe there is a good chance he clears waivers and comes back but I didn't like the risk.