Per the above paper, possibilites for delayed outflow:
1) "One possibility is that the jet was weak or inactive at early times after the disruption and then suddenly became activated at ≈750 days. Such sudden activation could result from a state change in the SMBH accretion disk, such as a thin disk that transitioned to a hot accretion flow." Tchekhovskoy et al.
2014
2)An alternative explanation is that powering a relativistic jet via the Blandford–Znajek process requires a strong magnetic flux threading the black hole horizon. The original magnetic field of the disrupted star in a TDE is not expected to contain a strong enough magnetic field to power a relativistic jet (Giannios & Metzger
2011), which requires an alternative origin. The first possibility is that the magnetic flux could be generated through a dynamo by the accretion disk itself; Liska et al. (
2020) found that it may take only ∼10 days to generate poloidal flux from the toroidal field through a dynamo effect once the disk is sufficiently thick, thereby connecting jet production to the disk getting thinner as the accretion rate drops.
3)"Alternatively, Tchekhovskoy et al. (
2014) and Kelley et al. (
2014) suggest that the required magnetic flux may originate from a preexisting AGN disk, which is "lassoed" in by the infalling fallback debris; because the matter falling back at later and later times in a TDE reaches larger and larger apocenter radii, depending on the radial profile of the magnetic flux in the preexisting AGN disk, this could delay the jet production."
4)Another possibility is that the delayed radio emission is due to the timescales for debris circularization and viscous accretion (Hayasaki & Jonker
2021).
5)It is also possible that instead the jet has been present for the entire duration of the TDE. However, due to the combination of the high density of the large cloud of circularizing TDE debris (e.g., Bonnerot et al.
2022) and the potential for jet precession (e.g., due to misalignment of the disk angular momentum relative to the black hole spin axis; e.g., Stone & Loeb
2012), the jet is initially choked. At later times, as the accretion rate and gas density surrounding the black hole drop, eventually the jet is able to propagate through the debris cloud and escape.
I will need some time to digest the above.