After their marriage to Draupadi in a very public event after a very open conflict, it is natural that the Pandavas fail to keep their identities hidden and the news travels far and wide.
Among the Kouravas, Dushasana tries to console Duryodhana, by claiming that that if Arjuna had not been disguised as a brahman, he would not have succeeded in obtaining Draupadi. This assertion is insupportable from the text, as Arjuna got a chance to attempt the test only after all the kshatriya kings and princes had failed at it. But since the text also does not explicitly talk of the failure of Duryodhana, or of Karna, alternate explanations can easily be imagined.
Consider, for example, a scenario in which Drupada first invites the brahman camp among all the swayamvara’s attendees to take the test. Since the test requires physical strength, he has good reasons to expect that no brahman can pass it. He is, thus, merely following protocol. Likewise, the brahmans are expected to refuse the offer, as Draupadi’s swayamvara is a high-profile event where they might not want to risk alienating the kings and princes vying for the princess’ hand.
But Arjuna (disguised, like his brothers as a brahman for this event) rises up to take the test. In the text, there is a mention of how Arjuna’s willingness causes a schism in the brahman camp. In any case, going by this theory, Arjuna is the first and the only one to attempt the test, and thus Dushasana’s utterance becomes true. This theory also neatly explains why Karna or the Kourava’s explicit failures at the test aren’t mentioned in the Mahabharata. It also explains why Kouravas feel aggrieved by the way the Pandavas won Draupadi’s hand in marriage.
Draupadi’s hand also comes with Drupad’s army. And this fact leads to considerable agitation among Dhritarashtra, his sons, and Karna. Duryodhana suggests multiple ways to destroy the Pandava’s growing prowess, including Bhima’s assassination, and another one where attractive women are to be sent to the five brothers to seduce them, so that Draupadi becomes disenchanted with them. Karna rejects such subtle strategies, calling out for an all-out war, his reasoning driven by the simple fact that the Pandavas are not ready for a total war at this point.
Dhritarashtra can’t decide what to do, and takes the question to Bhishma, Drona, and Vidura. After Bhishma and Drona argue for giving a share of the kingdom to the Pandavas, Karna insults the two by suggesting that they have malice (towards Dhritarashtra) in their minds. He exhorts Dhritarashtra for war, emphasising that the entire kingdom shall go to the party favoured by destiny. It seems that Karna has imbibed Krishna’s Gita lessons already.
Finally, Vidura convinces Dhritarashtra to accept Pandu’s sons as his own and give them half the kingdom. The Pandavas are invited back into the capital, and thereafter given the forest of Khandavaprastha to establish their kingdom. An amicable solution is thus arrived at.
(The writer is reading the unabridged Mahabharata)