  A puzzling population of extremely massive quiescent galaxies at redshifts
beyond z=3 has recently been revealed by JWST and ALMA, some of them with
stellar ages that show their quenching times to be as high as z=6, while their
stellar masses are already above 5e10Msun. These extremely massive yet quenched
galaxies challenge our understanding of galaxy formation at the earliest
stages. Using the hydrodynamical cosmological simulation suite Magneticum
Pathfinder, we show that such massive quenched galaxies at high redshifts can
be successfully reproduced with similar number densities as observed. The
stellar masses, sizes, formation redshifts, and star formation histories of the
simulated quenched galaxies match those determined with JWST. Following these
quenched galaxies at z=3.4 forward in time, we find 20% to be accreted onto a
more massive structure by z=2, and from the remaining 80% about 30% rejuvenate
up to z=2, another 30% stay quenched, and the remaining 40% rejuvenated on a
very low level of star formation. Stars formed through rejuvenation are mostly
formed on the outer regions of the galaxies, not in the centres. Furthermore,
we demonstrate that the massive quenched galaxies do not reside in the most
massive nodes of the cosmic web, but rather live in side-nodes of approximately
Milky-Way halo mass. Even at z=0, only about 10% end up in small-mass galaxy
clusters, while most of the quenched galaxies at z=3.4 end up in group-mass
halos, with about 20% actually not even reaching 1e13Msun in halo mass.
