Waste of a retention slot.

The Kings are not interested in acquiring a goaltender beyond this season. They'll finish the year with the guys they have, and possibly add a rental to backup Talbot if neither Copley nor Rittich work out (Lankinen maybe). They'll look for something long term next summer. Allen is neither of those things.

Possibly, but with no goaltender on the books for next season Jake Allen at $2.4M might work. The Kings do have the Canadiens old GM who would be able to give a honest download of if Allen would work with our system. But having two older goaltenders probably isn't what they are looking for this season, I agree with you in regards to this trade, but I do think the Kings are on the lookout for at least one goalie to reup for next season.

Seems like bad asset management to keep Monahan unless there are no good trade options.

It won't be someone like Allen. They'll look to acquire a long-term option (~4 years) on a decent payday, and a ~$1M backup like Talbot this season. Allen is too expensive to play the backup role, and not good enough to be considered for starter duties.