Remember, we haven't actually demonstrated we're taking this seriously. The President is different now, so people might doubt the new guy.The conspirators are small fry compared to mopping up the remnants of the Confederacy. We can capture them later - now that we've mollified DC by taking decisive action and demonstrated we're taking this seriously, we can start pivoting towards the first stage of reconstruction - dismantling the South's military power.
But the capitol isn't actively rioting. There's no need to perform at legitimacy, which is what a manhunt would be for - the longer we let the Confederates fester in the field the harder it'll be to dislodge them.Remember, we haven't actually demonstrated we're taking this seriously. The President is different now, so people might doubt the new guy.