I think there's a bit of revisionist history going on here. IIRC, Aiken and the Astros agreed to $6.5M pending a physical. Aiken went to Houston and was expected to sign for $6.5M and the Astros were not expected to sign Marshall because he committed to LSU already (I think). Then the medicals came back. That's when the Astros reduced the offer to $5M and extended the $1.5M offer to Marshall.

IMO, the Astros uncovered the risk with Aiken's arm and then reassessed the situation. They figured if they could sign Marshall, then he could be an insurance policy in case Aiken blows out his arm and can't pitch again. On the other hand, if they extend the $5M offer and Aiken doesn't take it, they still get the #2 pick this year. Either way, they have a contingency plan so they don't ultimately waste the pick if they sign Aiken to $6.5M, Marshall goes to LSU, and then Aiken blows out his arm. I'm actually ok with this strategy.

I do not think they approached this draft with the same strategy as 2012 when they signed Correa. They adapted once they had more information and I actually think they protected themselves pretty nicely from completely losing talent. The real criticism of the Astros came from agreeing to the $6.5M offer and then reneging on it. It came off as cheap and spend thrift.