Senator shouldn’t be a lifetime position, but if Hatch knew Romney would replace him, he should have stayed in the Senate, even if it meant he was in Biden’s or Feinstein’s or Leahy’s condition.
I think the Mormon church made the decision. Romney has money and gives a lot to the church so I think Hatch may have been asked to let Mitt run. Hatch was old school, decent and well respected. Mitt is the scum of the rarth.