IMO it is clear that the Steelers had no intention of re-signing Lewis.
I don't know if it because they still consider him immature - after all, the main reason that it took him so long to start was because of his own temper tantrum.
I don't know if it because they see Allen as the starter and don't like Lewis as the #3.
But they made no effort to get him signed prior to him hitting FA, they made no effort during FA, and they let him sign elsewhere at a reasonable price without making a move on him.
To me, it seems like they just did not want him.