I'm just taking a wild shot in the dark and saying that Andersen isn't really injured, he's just cooperating by being put on LTIR until the end of the season. Several factors to consider:
A) Leafs are suspiciously quiet about his status. Everyone from Auston to the zamboni driver were openly talking about Matthews' wrist, but Andersen's ... whatever? Not a peep, not even speculation.
B) As Sportsnet confirmed Dubas now has ~$5M in cap space to work with until the end of the regular season.
C) Campbell is now the starter, so ...
D) While, I'm not 100% clear on the cap implication for the playoffs, if Freddie can come off LTIR once they start, but if he does he backs up Jack - No one would expect a goalie to come back after a 2-month layoff right into a playoff start. Saves face for Freddie heading into free agency as he didn't "lose" his starting job, he was injured.
I'm no capologist so feel free to shoot down the cap-related part of this theory, but Campbell/Hutch can clearly handle the net for the balance of the season and the Leafs are all but locked into a playoff spot. 1st would be nice but they're thinking that even dropping to 2nd/3rd won't hurt their chances for a long playoff run.
As for the what-ifs, like Campbell gets injured over the next few weeks or into the playoffs? Freddie is miraculously healed and returns to the net (once the playoffs start he'd be taking full practices but "not quite ready" and so still on IR).
And another wild shot is Foligno will be the (main) player the Leafs target.