• prayojakau — the two who engaged / instigated
  From pra-√yuj — to engage, set into motion. The technical word for the cause behind a cause; in Mīmāṁsā vocabulary, the instigator of an action. Bhāgavata's verdict on Akrūra and Kṛtavarmā: they are not bystanders but engineers.
• bhaya - vitrastau — seized with fear, terrified
  Compound: bhaya (fear) + vitrasta (extremely frightened). Same fear-vocabulary as verse 11's bhīta but intensified. Gauḍīyas note: pāpa-karma's natural climate is bhaya — the conspirators end the chapter in the same emotional weather as their victim.
• vyūṣatuḥ — they went into exile / departed
  Perfect dual of vi-√vas (to dwell apart). The verb of voluntary exile. Bhāgavata's narrative pattern: those who break with Kṛṣṇa eventually depart from His dhāma, even if no one banishes them.
• dvārakāyāḥ — from Dvārakā
  Ablative of Dvārakā — 'the city of gates,' Bhagavān's seat. Gauḍīyas read leaving Dvārakā as a form of self-imposed asat-saṅga: removing oneself from the place where Kṛṣṇa walks is its own punishment.

Akrūra and Kṛtavarmā, who set the conspiracy in motion, slip out of Dvārakā the way smoke leaves a closing window — Śatadhanvā's death frightens them into the same exile they had imagined for their target. Gauḍīyas read this as the lawful symmetry of pāpa: the engagers (prayojakau) inherit the fate they engineered.