Although Kyle Davidson has a plethora of young defensemen on the rise, it's possible that having a player with back to back cups could help mentor them. He's a bigger guy, which is also something Davidson seems to appreciate.
Rutta also seems relatively inexpensive; his contract with the Lightning was a 2-year, $2,600,000 with a $1,300,000 cap hit. His asking price might go up after being a part of a possible threepeat cup-winning team. If Chicago prioritizes him it's possible he might want to make a return, and if he's offered enough money.