  Understanding the mechanisms underlying many-body quantum chaos is one of the
big challenges in theoretical physics. We tackle this problem by considering a
set of perturbed quadratic Sachdev-Ye-Kitaev (SYK) Hamiltonians defined on
graphs. This allows to disambiguate between operator growth and
\emph{delocalization}, showing that the latter is the dominant process in the
single-particle to many-body chaotic transition. Our results are verified
numerically with state-of-the-art numerical techniques, capable of extracting
eigenvalues in a desired energy window of very large Hamiltonians, in this case
up to dimension $2^{19}\times 2^{19}$. Our approach essentially provides a new
way of viewing many-body chaos from a single-particle perspective.
