I honestly cannot claim to be well-informed on that. I have read some things over the years essentially saying there was a much bigger web of co-conspirators involved, but there are just so many unanswered questions still that I don’t have a clue.
He was widely reported to have had an active plan to assassinate GHWB in ~93 or so in I think Kuwait, so it isn’t totally out of the realm of the possible, though honestly I would think that if he get involved in something, it would send a more clear message from him than a big building in OKC.
You might check out Jayna Davis
http://www.jaynadavis.com/