You only made one mistake, and it impacts oxygen, which in turn impacts the depth of oxygen into the soil, which of course impacts the depth of oxygen dependant activity in the soil to the degree that is does or does not impact your plants. A lot goes on in those upper layers where heat and the atmosphere penetrate the upper few inches of the soil horizon.
You made the leaves smaller.
Two things would have happened if you had not.
1) As you seek an insulator, the forest floor has worked it out to have loose , large leaves in fall with plenty of air pockets. Here is where insulation comes in. Loose puffy parka jackets, fiberglass batt insulation etc are all trapping air. Conductors are solid, insulators puffy.
2) Those loose leaves get air as close as possible to the soil, thus as deep as possible into the soil. By matting them, and prematurely wetting them possibly, you have not only reduced insulation prematurely across winter, but increased to some degree a suffocation of the soil below.
Solution: Study the process of the forest floor. There is a fall-winter-spring timing already worked out in the way leaves collapse and become compost. Be lazy. Getting the leaves to the spot was good enough. Do not overdo the pile height either.
