Red nuggets pack a giant elliptical's stellar mass into 1 to 2 kpc, already quenched at z of 2 to 3 (Damjanov 2009; van Dokkum 2015). The model needs extreme early collapse, then total shutdown, then factor-of-several inflation by tuned dry mergers, while sparing the few compact relics that survive un-puffed, four stages with four separate stories.
Hierarchical assembly builds galaxies gradually and gently, so every nugget property must be engineered: dissipation beyond the models for the density, feedback choreography for the quenching, merger diets for the growth, and merger luck for the survivors. The ensemble has no unified mechanism because the framework never expected such objects.
SCT runs the whole life cycle on two mechanisms. Formation and quenching are one step: a low-impact-parameter seeding event deposits its baryons dense and centrally concentrated, with little angular momentum (P22, P25, P33), so star formation runs hard on the compact reservoir and exhausts it early, while the cascade-seeded central black hole (P46) matures alongside rather than after its host. Born dense, burned bright, finished early: the quiescent compact massive combination is the natural endpoint of a head-on deposit, the same seeding physics behind the quenched z of 7.29 population that outruns every simulation by orders of magnitude (recid 113 territory) and the early-mass crisis (recid 107).
The growth and the survivors are the M5 half: nuggets inflate into today's ellipticals as their galactic tensor mesh loosens, the canonical inside-out growth of Paper 7, From Chaos To Cosmic Expansion, with the matched R_e scaling near (1+z) to the -1.0 to -1.5 (recid 119). The mesh weakens fastest where ex-situ accretion feeds the envelope, so nuggets in dense environments puff on schedule while the rare relic in a quiet corner, accreting little, keeps its mesh taut and its radius small. The survivors are not exceptions to the mechanism; they are its low-accretion limit, predicted rather than excused.
Keystone economy: P33 makes the nugget, P14 unmakes its compactness on a measurable schedule. Four ΛCDM stories become two SCT mechanisms.
JWST nugget spectroscopy carries the formation kill: stellar populations showing extended, gradual formation histories rather than the fast early burst a dense deposit demands would refute the head-on origin. The growth half is testable through the survivors: SCT requires relic compactness to anti-correlate with environmental accretion history, taut mesh in quiet corners, while merger-luck models predict survivors scattered independent of environment; a relic population uncorrelated with environment would break the mesh-loosening account.