I firmly believe Sessions viewed both Obama appointed Ag’s Holder, and Lynch, violated their sworn constitutional obligations and even assisted and advised Obama when he began doing so. Because they did, their actions deeply affected Sessions recusal decision. If that was one of his reasons for recusing he should be bringing this up and deflect these political attacks even if it does mean opening up a new can of worms from the Demo cannery.
Sessions was working with the conflict management people at DoJ from January until March, I'm sure not full time, but questions of what he might have to recuse from were flying around and would have to be addressed eventually.
It turns out that he would not be seen as unbiased in a case involving the Trump campaign. As the French say, "quelle surprise!" A parallel univers AG Podesta would not be seen as unbiased in a case involving Hillary, either.
Session's recusal is by the book. If there was not a regulation "on point," I doubt he would have recused from an investigation into criminal conduct by the Trump campaign.
My point is that I don;t think sessions recusal was affected in the least by the conduct of Holder and Lynch. The simple fact is that a person who was part of the campaign won;t be seen as unbiased if asked to judge the campaign.
Trump's fate in this battle does not depend on Sessions, he has plenty of other soldiers to draw from. And Sessions would have a tough time fighting this battle, just like Lynch would have a tough time fighting a battle to protect Crooked Hillary.