The very short of it is that the “flavor components” are locked behind the cell wall of the tobacco plants structure, because that is the way mother nature solved many of the problems that confront a living plant: “the plant cell wall plays a wide range of physiological functions, which include the defense system against pathogens, translocation of nutrients (in this case ‘flavors’), and transduction of chemical signals within plants, and the mechanical physical structure or the plant itself.”
So you want to get those great tobacco flavors into your vape juice to enjoy? Well, then you have to beat mother nature at her own game. That is going to require disruptions of the cell wall. So things like Heat, mechanical destruction of the wall itself (ultrasonics are commonly used for this approach), and enzymatic chemicals, are all ways to work on the problem at hand. Time works, sort of, but without breaking through the cell wall you might have to outwait mother nature, which is always an ‘iffy’ proposition. Just ask any cat.
There are very good references to this subject all over the net . You can start on a background discussion of cell walls at Wikipedia, then move on to research paperss for tobacco plants with things like this: Cell Wall Dynamics in Tobacco
I want to add that the very clever insight that @Kinnikinnick saw with his “hot bump start” is that the initial heat shock to the cell wall provide sufficient disruption to maximize the effective use of the later ‘closet soak’ time. It works very well because of valid technical reasons.