Here in the original manuscript, Oliver Cowdery corrected now with for; he crossed out the now that he had initially written and supralinearly inserted the for (and without any change in the level of ink flow). The for works much better than now in this context since its associated clause is explanatory. We would expect now to introduce a new topic. Oliver’s initial error here in verse 34 was probably the result of the subsequent use of now that begins the following verse: “now Zeezrom saith unto the people” (Alma 11:35). The critical text will, of course, accept Oliver’s corrected reading in 𝓞.
Summary: Maintain the use of for in Alma 11:34; in this case, the for explains why the Lord will not save his people “in their sins”.