@Chili
Krishna wanting Arjuna alone fails to explain how it would make him Krishna's tool. Unless Panchali were conspiring with Krishna, it would make Arjuna Drupada's tool.
Forget my objections to polyandry or upapandavas, that theory doesn't compute even accepting text as is.
Also, FP is right that being daughter or sister to Yadavas wouldn't make them not participate as they had a lot of intermarriage. The only reason would be that they knew she was meant for someone else. If they all knew not to participate, then Krishna planning this alone only to get Arjuna doesn't compute, does it?
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Krishna allowing the massacre also assumes Vaishampayana lied when he said Krishna told the Pandavas everything after he returned to camp.
It fails to explain why Krishna's inyel says Ashwatthama intended to attack Pandavas when the target was Dhrishtadyumna and the upapandavas.
It ignores why Dhritharashtra and Gandhari wouldn't use the information to taunt the Pandavas back when taunted. It fails to explain why Vyasa woildnt.
It assumes Pandavas stayed deliberately away when CE says nothing of the sort. If they heard the intel as text clearly says and stayed away, only 2 possibilities are 1) they were killing their own sons which is unlikely or 2) their camp was different.
It fails to explain why Panchali turns conveniently dumb at points in her life only to turn super intelligent at points which suit Krishna.
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Bottomline is both theories work only in a vacuum where no one else reacts. And that is not possible in a real world. Krishna would've known it was impossible to control all elements in a scheme like you described.
Basically both theories would work only if Krishna were omnipotent and omniscient. In other words, God. But as God, he wouldn't need the tricks.