I think his boasts overstated his Islamic terrorist connections, but I think they stated the truth of his allegiances and his motivation for the Islamic terrorist attack that he committed.
Well said.
At the end of the day, my bet is that OM is an example of somebody responding to a call for "leaderless resistance" attacks. In these types of attacks, the call (ISIS propaganda) is very clear. Those independently responding to the call, however, can have mixed motivations. varying levels of intelligence, and varying degrees of emotional stability. But... they all respond to the call in their own way and the call is their main motivation.
As a side note, leaderless resistance terror attacks are very hard to stop because there is no leader, large formal groups etc. In addition, leaderless resistance as a concept was first advocated by far right and far left activists here in the USA. For example, Earth First has made such calls for attacks against property (they just have not had that many takers). As with ISIS, those responding to Earth First calls have had varied levels of brain power.