The time for that was what we already saw in the lead-up to the midterms. The midterms were, in turn, an even louder dog whistle. Or, better, wet blanket, putting out most of that fire.
And now Mueller is methodically, strategically releasing any remaining pressure from the cooker out slowly, with each successive (escalating) revelation. He is VERY aware of the same potential and is clearly taking steps to avoid it.
Does that mean there won't be some Steve Banon-types trying to kick up some excuse for violence? Of course not. I'm sure there are many knuckledragging beta cucks out there who wish they had the balls to do something and many other nut-jobs with the screws loose to actually try something, but the midterms kicked most of them in those balls in a way that is far more effective. It was undeniable.
So that takes care of a good 70-80% of any such possible fanatic reactants, leaving a still volatile 20-30% or so. But that's 20-30% of like a total of 10% of the population (or less). And that's still not good, but again, that's who Mueller is keeping in mind in his slow, methodical and inexorable approach. He's already surrounded them and laid down suppressive fire and is slowly pushing them--along with Trump--into ever tightening concentric circles, forcing Trump in particular into a corner that he can't escape from unless he goes through Mueller.
I have no doubt there will be a few attempts and even a few successful events (doubtful they would be as large as Oklahoma, but certainly possible).
But, again, it is the Republicans that are keeping the Mueller investigation going, not the Democrats (they don't have that power yet), so that means among the higher echelons of right-wing power it has already been agreed that Trump is to be eviscerated. And sitting prominently among that right-wing power are all of the military and intelligence communities that Trump has repeatedly shat on throughout this whole debacle. Which means that any such activity would be rogue activity, not sanctioned by the higher ups.
Again, certainly a possibility, but we've clearly gone from Defcon 1 (before midterms) to Defcon 4 (after) in regard to any such activity.
I think the biggest worry would be--as you noted--an assassination attempt against Mueller, but even if that were to happen, it would only strengthen the fire against Trump, not put it out, so any such attempt would therefore likely only come from the truly desperate screw loose nutjobs and thus have a very low probability of success (and something Mueller is likewise already well-aware of).
My guess would be that if we ever see anything like an Oklahoma style attack, it would be an
attempt that will fail (precisely because it would be conducted by desperate morons and not higher level professionals) and only then if we ever get to the point of impeachment in the House, which I think unlikely. Trump will likely resign before that actually happens.
Remember, by then, we will have gone through
months (possibly years) of extremely detailed and relentless witnesses--one after another after another after another--talking for hours and hours and hours about all of the crimes Trump has committed throughout his entire lifetime.
I'm talking about shit that would make the "pee" tape look like a Skinemax soft-core porn. Trump considered Roy Cohen his "mentor" and Roger Stone a close friend. Allow me to use Oliver Stone to illustrate what that would look like on a regular basis for years:
Think of it this way, where we are NOW is about a hundred yards up Mt. Everest. We haven't even
begun to get anywhere near the summit of what is about to happen in this country. So you have to look at it from the perspective of being
on the summit looking down, not at the base looking up.