This is one case where even if Baldwin had inside dope and indiscreetly revealed some it wouldn't have made much of a difference. They knew we were coming and had a plan. We knew they were waiting and tried to soften them up. With very little success as it turned out.
True. One has to wonder, would it have been just as difficult if we'd just skipped the pre-invasion bombardment?
I think so, but it still wouldn't have given us the element of surprise. The Nimitz Graybook has been very illuminating about the pre-invasion airstrikes on Iwo to neutralize its airfield. Plus, there have been airstrikes against most of those islands' installations for months. Taking one of those islands is the next logical step toward the home islands.
I don't think the technology of the day had the means to "soften up" Iwo because the bunker network was too deep and too extensive to penetrate and destroy. It is a sad thing to contemplate as we know the sacrifice that is about to be made.