Removing Duplicate Nested List Levels – R Studio

I have a list where one of the levels is duplicative and unnecessary. The first level is a list of unique accounts, which are each lists containing fueltype, fuelunits, description, modeltypes, and usagedata. The previous four are single value descriptors, but usagedata should be a list of 12 observations. Instead, there is an additional level between usagedata and the observations. I cannot figure out how to unlist or flatten this such that usagedata is a list of 12.

Image of Nested List Hierarchy