Yang was a disruptive element....

While he was on "their side" more or less, he would have disrupted their plans and possibly stumbled into their plans and then because he seems to have a somewhat working "conscience" he would have definitely exposed them.

If Yang would have been elected they would have JFK'ed his ass.

Just think, they would want him gone, plus all the leftist support by making him a martyr.... and the deliciousness of pinning it on some "right wing kook"...