He’s not a lawyer.
True but high level agency positions are political/managerial ones in nature. All they require is approval by the senate.
There is no formal or Constitutional requirement for an AG to have a law degree, nor their deputies.
One similar example is the position of Surgeon General. They do not have to be a surgeon (and that has been the case before).
In Navarro’s case, not being a lawyer could become problematic for him, but its not firm road block either.