“I mostly recall those two aforementioned FReeper factions — Santorum and Gingrich — sniping at each other frantically through March and April.”
FR became a haven for Gingrich supporters and that was that. FR helped Romney as much as anyone else. Gingrich staying in the race allowed Romney to win in Michigan, Ohio and Wisconsin - states that Santorum needed to win.
Gingrich nearly let Romney win in Mississippi and Alabama! Aside from South Carolina and his homestate of Georgia, that was that.
FR has nobody to blame but itself that Romney is the nominee. They could have backed a conservative who could have beaten him, but they didn’t. So he lost, and that’s that.
Pretty difficult to agree on a candidate when they all had major flaws, and there wasn’t a candidate that stood clearly above the rest. You want to blame somebody, then blame the candidates.