This instance of etc. was deleted in the 1920 LDS edition. The etc. is actually necessary since there were other things besides idol worship that these apostate Zoramites had started to do. In fact, much of this chapter describes in great detail the worship practice of these Zoramites (which, it should be noted, has no specific reference to bowing down to idols). David Calabro points out (personal communication) that the tidings that Alma received may not have been fully accurate. On the other hand, we needn’t presume that Mormon’s abridged record included a complete account of the Zoramite apostasy. In any event, the critical text will restore the original occurrence of etc. here in Alma 31:1.
Summary: Restore the original etc. in Alma 31:1 since the text intends to say that Zoram was encouraging various apostate practices in addition to idol worship.