Team set a franchise record with Galchenyuk as #1C in 2016 getting 19 points out of a possible 20 over the first 10 games of the season. They were also the #1 team in the NHL right up until Galchenyuk injured his knee in December.
Supporting cast type players played over their heads during that 10-game period. It was completely unsustainable for them, as proven shortly afterwards. That's, ultimately, what permitted MON to have a franchise record start to the season, not Galchenyuk carrying the team on his shoulders like a Viking God going to war.
Your statement is observational and, had it rained solid during those ten games, as valuable as stating that MON played great because of the rain.
I'm not saying that Galchenyuk didn't have a great offensive start to the season that year, before his injury, but the conclusions that are quickly made, with no real analysis to that start of the season, are somewhat empty, IMO.