Guards are our weakness in the O-line, specifically RG. There is no reason to go after a RT when RG is our major weakness.
Not that Loadholt is an upgrade, but your statement (imo) isn't true.
There's no "first this, then this" in terms of building a team. Yes, some needs outway others, but if there's an upgrade available, a team won't ignore it.
It's not like PC and JS say to themselves "we can't even think about upgrading RT until we fix RG" or "we can't get a WR until after we get a DT"