The secret, horizonhb, is that the Greek word that expresses cause (γὰρ) is always postpositive — that is, it has to come second in a clause, where we would put our cause-word (because, or for, or since) first in the clause. There are many such postpositive conjunctions in Greek — it's a peculiarity of the language, and is usually learned in the first few weeks of any ancient or biblical Greek course.
So γὰρ really does mean "for", not "indeed."