Srimad Bhagavatham says,
The day when Shishupala and Rukmini's wedding was decided, Shishupala and his supporters (Śālva, Jarāsandha, Dantavakra and Vidūrath SB 10.53.17 ) said if Krishna and Balarama comes here and try to take away Rukmini then they all will fight against them.
To secure the bride for Śiśupāla, the kings who envied Kṛṣṇa and Balarāma came to the following decision among themselves: “If Kṛṣṇa comes here with Balarāma and the other Yadus to steal the bride, we shall band together and fight Him.” Thus those envious kings went to the wedding with their entire armies and a full complement of military conveyances. SB.10.53.18-19
But, Rukmini sends a trusted brahmana with a message to Krishna in which She express her love for Him and asks Krishna to marry Her. This message was confidential which was between Rukmini and Brahmana only.
The brāhmaṇa said: This is the confidential message I have brought with me, O Lord of the Yadus. Please consider what must be done in these circumstances, and do it at once. SB 10.52.44
My questions is:
If Rukmini's message to Krishna was confidential then how could Shishupala and his supporters even think Krishna would take her away? Was there any link between Krishna and Rukmini earlier which was known to Shishupala or others that made then think so?