What's the Day of Judgment got to do with it?

Henning Mankell's The Man From Beijing finally came to the top of my to-read pile, and I'm enjoying it as much as I'd hoped. But this one sentence caught me this morning. The protagonist is recalling her youth as a member of a Maoist youth group in Sweden and comparing it to having been brainwashed by a religious cult.

We were not urged to commit collective suicide, because the Day of Judgment was nigh, but to give up our individuality for the benefit of a collective intoxication, at the heart of which was a Little Red Book that had replaced all other forms of enlightenment.

I firmly believe that comma - the one after "suicide" - is in error.

The reading we have is that "because the Day of Judgment was nigh" is the reason they were not urged to commit suicide. That doesn't make much sense to me. Instead, I believe it to be the motive for the suicide they weren't urged to make - that is, committing suicide because the Day of Judgment was nigh (as a religious cult might do) is the thing they weren't urged to do.

Punctuation is almost always a cohesive device rather than grammar. Just as conjunctions do, it explicitly tells the reader how to connect the elements of a sentence. Here, the comma tells the reader to connect them wrongly (at least I think so).