Edited Apr 25 at 12:56
I think this makes sense. Only one year and less expensive then his previous contract (He signed 2Yrs/1,65M with Ottawa). Thompson stated many times that him and his wife absolutely love the city of Montreal and he seems to get along well with other players like Tatar and Domi so that makes him a motivated player.
It also makes sense in terms of the lineup because it takes out Deslauriers or Peca off the top-12 assuming we sign Lekhonen and Weal.
That's how I think they see it AS OF TODAY (there migh be changes during summer) :
Tatar - Danault - Gallagher
Drouin - Domi - Shaw
Lehkonen - Kotkaniemi - Byron
Weal - Thompson - Armia
Scratches : Deslauriers, Peca.
Another factor might be that MB and CJ really disliked how it went with the 4th line last year. (Remember, we saw guys like Agostino, Chaput, De La Rose, Deslauriers, Hudon, Peca, Scherbak and Weise)