I am also an english learner,I just try to answer your question.
1."itself' indicates the environment.
2."they" indicates the events so impressive.
I think the sentence means "Even though we have the excellent skill of detecting and connecting anomalus events ,the skill can not help us understand events so impressive,which are readily noticed-but not easily explained"
3.I do not know what is your question about this sentence.
Student or Learner