I'm sure getting rest is the main reason, healing any nagging soreness that comes with playing sports professionally. Reduce risk of an injury that could hamper his play.
But I also think that the Nashville games presented a weird situation. Winning (or more accurately Nashville getting zero points) made it far less likely they would play one another in the post-season while needlessly losing would give Nashville confidence if they could go 3-0 against their playoff opponent. Regardless of how well a small sample size in regular season translates to the playoffs ala Calgary vs Colorado in 2019.
So, and especially with yesterday's game, they had to set the stage and treat this game as a statement game in terms of physicality, matching them offensively and defensively, but stopping Nashville from getting two points wasn't a concern.
Put in Vladar, try to outplay them, but if they lose the game, oh well, you can convince the team that Nashville won in a near do-or-die situation for them against the team's backup in a meaningless game for the Flames. Now, inversely, the team wins in OT and they can go into the playoffs against their likely-opponent having just beat them a week before (despite playing their backup) while outshooting them 38-23 and (nearly) matching them hit for hit (36-38). Not to say that they were playing for an OT victory, but it's probably best case scenario for result. An outright win is nice but then the Flames just played a physical playoff-like game against a team they won't see in the playoffs.
More important question is "Where's the November 2nd games NHL?" They have purged those games from existence:
https://www.nhl.com/predators/schedule/2021-11-01/CT
https://www.nhl.com/flames/schedule/2021-11-01/MT
https://www.nhl.com/scores/2021-11-02
Where’s Jacob Markstrom?
