When all this started two months ago, I spoke with someone that I consider to be an expert in planetary infantry operations (as opposed to microgravity) and counter-insurgency work. They told me then that successful counter-insurgency operations means presenting overwhelming force on the ground—close to 10 ground troops for each insurgent combatant—and a containment strategy that gives the majority of the population not in open revolt clear incentives to remain not in open revolt. Optimally, this is one that uses carrots, not sticks, as sticks also provide incentives to radicalize. You also need to make sure that word of this incentivization (and, ideally, the incentivization itself) spreads to areas not already infected with the insurgency, or they will be.
At no point did the Khanid response include any of those elements. The results of this are not surprising.