This doesn’t mean that Cruz was an Islamic jihadi. It means that he saw their bloodlust, and admired it. An organization that glories in violence and murder is going to attract people of like mind. And if that organization justifies itself by reference to the teachings of a major religion, this kind of thing is going to keep on happening.
The FBI, of course, did nothing. I can hear the clueless agents now: “ISIS? Pah! They believe in jihad, an interior spiritual struggle!”