Congratulations on the hire, difficult to know if it will work, but the stars are aligning a lot better than in Monaco for Henry, that's for sure.
Some more info on the Monaco thing: the big picture is that the club is owned by a Russian billionaire who has been involved/accused of being involved in a dodgy art dealer situation for a few years. He tried to influence the outcome by allegedly influence the interior minister of Monaco which left the Prince very displeased. So turmoil in Monaco, and as a consequence, turmoil at the club at that time as the prince forced to regain influence within it (hiring & promotion of a grandson).
At a sporting level, the club has had great success with Jardim and a couple of squads that involved guys like Bernardo Silva (now key player at City) and MBappe; on summers 2016,17 & 18, the GM sold at for absolute fortune most of the players to invest in promising young players. This was the concept: get young promising 'starlets', play them for a year or two and sell them. Nothing romantic about it.
This left the squad with some potential last year but question marks, and a rather thin roster in terms of leadership: the team sank under Jardim. He got sacked with the team towards the bottom of Ligue 1 & that's when Henry was hired. The team was already in disarray and injuries kept mounting (not trying to make excuses for Henry here, don't get me wrong) including the last talisman Falcao.
Henry was unable to stop the bleeding and some games were hampered but stupid sending off - those young players were struggling to cope with the pressure of the league position, perhaps even struggling with the pressure of the extra spotlight/media attention that Henry's first manager position, brought.
Henry did not demonstrate much ability in sorting this mess out to be honest. There were some moments where he did not seem to connect with the players - there also were conflicting influence in the locker room with some more senior players still very unhappy with the Jardim firing.
By the time the January transfer window came, the team was in no better league position. Falcao finally recovered from injury, and Henry was granted his wish in getting Fabregas in. But within a few days of that happening, and with strange timing, he was sacked. Oh and Jardim returned. Make what you want of that and Monaco's current management/ownership (Monaco is a great/historical club and this whole mess feels very unsuited).
I think this second manager experience will be helped by starting a season fresh (not in the middle of it) and have a chance to influence how the squad is built from the get go. He will want experienced players and players who know how to behave professionally; he will relish not to have to be a father figure.
He is very much a north american guy now, he loves it (he was at Tony Parker retirement ceremony in San Antonio this week). And I really believe that he is very excited about Montreal.
He is a London kind of guy and dull/rich Monaco, not so much for him these days. I think it is significant that he has already mentioned that he is looking forward to engaging with the multicultural aspect of the city and its people. He is going to feel a lot more at home with you, I can tell you that.
Anyway let's hope for the best. There is no certainty about this aside that he needs for this to work, and he is a determined & extremely competitive guy, and deserve some trust.
Good luck to all, à la votre!