I don't think they're necessarily trying to have enough moral high ground to justify a genocide, just vaguely enough factual events that they can convince people there was a legitimate reason to engage in a legitimate war, and that there's a worldwide antisemitic campaign to pretend it's not a legitimate war, and that there are enough antisemites that they've managed to capture the whole UN etc.. Whether or not that's the goal, it's a pretty widely-held belief worldwide that the Irsaeli government's obvious lies are more plausible than factual claims about Palestinian civilians dying, and everyone accusing Israel of genocide is a lying antisemite is the easiest way to reconcile the conflicting information without landing on the country whose ministers are tweeting genocidal intent and that blocks independent journalists accessing Gaza is probably doing a genocide.