  We give an new, elementary proof of the result that the smallest non-cyclic
quotients of automorphism group of free group is the linear group over the
field of two elements, and moreover all minimal quotients are obtained by the
standard projection composed with an automorphism of the image. This result,
originally due to Baumeister-Kielak-Pierro, proves a conjecture of
Mecchia-Zimmermann.
