Doesn't it depend on the region? To my understanding, in the north, the upper classes were with the British. In the South and Mid-Atlantic, it was the slave-owning plantation elites (ironically enough) who were the most in league with the Patriot cause, with the lower classes being more divided in their loyalties.
Though I confess I am not sure why they cast their lot with the Patriot cause -they had the most to lose knowing the British would (and certainly did) use their slaves against them.
It helps to go state by state and look into the divides that existed between upper and lower classes over the decades leading up to the Revolution. This would help explain why in some states you had reversed dynamics.
Settlement patterns is another factor and religion as well.
In Vermont for instance the state was already in rebellion against New York landowners and the Royal Government of New York who had claimed the area for themselves, which also conflicted with New Hampshire.
North Carolina had an uprising in the Western part of the state just prior to the war as well, with similar vibes to the Whiskey Rebellion in PA 30 years later.
PA was still technically a company owned by the Penn family when the war broke out. This of course leads to all kinds of issues and lower class resentment.
New York had various tensions between Dutch land owners and English lower class and also English land owners and English or non-English lower class (not to mention of course spill over to Vermont).
In MA you had a strong lower class element, but people like John Hancock were already thwarting British trade polices via smuggling and then with the crippling sanctions on Boston there was even more incentive for wealthy merchants, fishermen, as well as farmers and laborers to join the patriot side. Closing Boston harbor was very destructive economically.
