  Very recently, the CMS Collaboration reported a peaking phenomenon existing
in the di-$J/\psi$ invariant mass spectrum from $pp$ collision, by which the
$X(6900)$ structure announced by the LHCb Collaboration was confirmed, but also
more enhancement structures were discovered. Facing such a novel phenomenon, in
this work we indicate that these new features reflected from the CMS
measurement provide a good implication for a dynamical mechanism which
reproduces the novel peaking phenomenon in the reported $J/\psi$-pair mass
spectrum well. This mechanism is due to special reactions, where different
charmonium pairs directly produced by $pp$ collision may transit into the final
state of $J/\psi J/\psi$. The present work provides a special viewpoint to
decode these observed fully charm structures in the $J/\psi$-pair invariant
mass spectrum.
