I'd rather take a no-risk flier on someone like Randolph (who has upside based on tools, age and performance in limited minutes) than stick with a guy in Crawford who's only decent and won't be part of the next excellent Blazers team (whenever that might be).
I don't believe in tanking, but trading superfluous veterans for players who have at least a sliver of a chance of breaking out? Sure. I noted that with Aldridge in the fold and playing like a star and the possibility of Batum being in the process of breaking out, if you can get a solid (not star) point guard and center, you're a lucky break from a contender (that lucky break being finding another star player). Randolph could be that lucky break. Probably not, of course, but doesn't hurt to see, IMO. If Randolph does pan out, you can make room. He could play small forward with Batum at shooting guard, or he could play power forward with Aldridge at center. It would be a "good problem" to have.
Again, not saying it's likely that Randolph will finally bust out into a star with Portland, but I think there's a non-trivial chance.