If Trump fires Session, there will be significant reverberations. It’ll be a revolt that will make the past six months seem like a honeymoon. It would be a major mistake. Pray he doesn’t do it.
Trump knows that the Mueller investigation is an existential threat. Not because of collusion with criminal conduct but because Mueller is unaccountable. Left in place, Mueller will dig and dig and dig and eventually make accusations that will at a minimum prevent Trump’s reelection. Trump needs an AG who will fire Muller. It is that simple.