SB 10.57.4

yo ’smabhyaṁ sampratiśrutya
 kanyā-ratnaṁ vigarhya naḥ
kṛṣṇāyādān na satrājit
 kasmād bhrātaram anviyāt
Synonyms: 
yaḥ — who; asmabhyam — to each of us; sampratiśrutya — promising; kanyā — his daughter; ratnam — jewellike; vigarhya — contemptuously neglecting; naḥ — us; kṛṣṇāya — to Kṛṣṇa; adāt — gave; na — not; satrājit — Satrājit; kasmāt — why; bhrātaram — his brother; anviyāt — should follow (in death).
Translation: 
“Satrājit promised his jewellike daughter to us but then gave her to Kṛṣṇa instead, contemptuously neglecting us. So why should Satrājit not follow his brother’s path?”
Purport: 

Since Satrājit’s brother, Prasena, had been violently killed, the implication of “following his brother’s path” is obvious. What we have here is an assassination plot.

It is well known that both Akrūra and Kṛtavarmā are exalted, pure devotees of the Supreme Lord, so their unusual behavior requires some explanation. The ācāryas provide it as follows: Śrīla Jīva Gosvāmī states that Akrūra, although a first-class, pure devotee of the Lord, was a victim of the anger directed against him by the residents of Gokula because he took Lord Kṛṣṇa away from Vṛndāvana. The gosvāmī further states that Kṛtavarmā had associated with Kaṁsa — both of them being members of the Bhoja dynasty — and thus Kṛtavarmā was now suffering from this undesirable association.

Śrīla Viśvanātha Cakravartī offers an alternative explanation: Both Akrūra and Kṛtavarmā were furious with Satrājit because he had insulted Lord Kṛṣṇa and spread false rumors about Him in Dvārakā. Under normal circumstances Akrūra and Kṛtavarmā would have been most pleased that Lord Kṛṣṇa married the beautiful Satyabhāmā. Being pure devotees, they could not actually be unhappy about this match, nor could they become jealous rivals of the Lord. Therefore they had an ulterior motive in behaving like His rivals.