1) it is not hard to get a silencer. You can make one in under an hour with cheap parts from a hardware store and a drill.
2) the CEO was at a conference. It's not surprising that this person "knew he would be there", it's interesting that this interviewee stresses this point like it is some big one to be made. The CEO of a big company in an industry will of course be at a big industry conference. You can say "how did he know he would be exiting that door" or something, but it's not like he was sneaking out the back exit. Hes probably coming out the door where the limo is parked or whatever.
I agree this was probably not a professional hit, but this was very clearly well planned out with limited knowledge. I don't think it's as simple as a disgruntled family member of a medical patient or something. It's likely this was something much more serious, but not billionaire behind the scenes business politics or something. Those kind of guys, while we like to pretend would be the last guys to know where to find professional killers, they all know where to find professional killers. I'd guess this guy was into something he shouldn't have been into with some unsavory people.