Speculation, but if I was a Trump advisor, my thinking would be this:
If Trump takes action and clears out the autonomous zone, is he going to sway any votes? Probably not. Those who support him will continue to do so, those who don't will continue to oppose him. The media will cry oppression and twitter will freak out for a week or so
If he lets it remain, and lets people draw their own conclusions about the zone and the politicians that enable it, he may sway a few votes naturally
Who really knows, though