This is the def of irrationality - Irrational behaviors of individuals include taking offense or becoming angry about a situation that has not yet occurred, expressing emotions exaggeratedly (such as crying hysterically), maintaining unrealistic expectations, engaging in irresponsible conduct such as problem intoxication, disorganization, or extravagance, and falling victim to confidence tricks.
But he did in fact have unrealistic expectations.
He wants, does he not, to advance his agenda? And his excuse for his murders is that he committed them in the hope of so doing. And yet the fact is that his actions will not advance his agenda. Instead, it will associate his agenda with murder and hate and death. His actions will, if they have any effect at all, work against anything he thinks he wants to achieve.
When Panda asked you: "So he chose targets that also hurt his cause?" you replied: "Essentially yes."
So as an example of rationality, it's on a par with McDonald's trying to sell hamburgers by taking out ads saying that they kick puppies to death and then grind them up for hamburger meat. It's asinine.
His expectations that his murders would help his cause are as unrealistic as unrealism can be. And by the definition that you yourself have supplied, that is irrational thinking.