It was absolutely a weird plot but it can have a meaningful explanation within the naruto's universe logic.
Hagoromo was connected with Sasuke and Naruto because of their chakra connection with ashura and indra. The trigger was their close death experience. In their meeting with Hagoromo, Hagoromo was able to give them his own power. This logic explained and accepted in Naruto's universe. He was sage, juubi jin, a time transmigrant...
And now... Obito and Kakashi's chakras had become somewhat similar to Indra-Ashura-Hagoromo's chakra. It is probably due to their sharingan connectedness. We know that they can see their eyesight in sometimes and their sharingans transformed into mangekyou at the same...etc. What about the trigger which connects them now? It is the kamui. Look at the picture:
You can see that something in form of chakra or a form of spirit is touching Kakashi and then he connects with Obito. That thing is kamuied by Obito to the living beings world. He was in a world like Kakashi had been in when he was killed by Pein and where he met with his father. In that world, Obito's chakra hasn't gone yet and he somehow used kamui to trigger the meeting with Kakashi or the reason behind his capability of using kamui maybe that at the end he became a juubi jin for some time, let him give some sage art.
Btw, I do wonder whether Obito got blind or not!
Hagoromo was connected with Sasuke and Naruto because of their chakra connection with ashura and indra. The trigger was their close death experience. In their meeting with Hagoromo, Hagoromo was able to give them his own power. This logic explained and accepted in Naruto's universe. He was sage, juubi jin, a time transmigrant...
And now... Obito and Kakashi's chakras had become somewhat similar to Indra-Ashura-Hagoromo's chakra. It is probably due to their sharingan connectedness. We know that they can see their eyesight in sometimes and their sharingans transformed into mangekyou at the same...etc. What about the trigger which connects them now? It is the kamui. Look at the picture:
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You can see that something in form of chakra or a form of spirit is touching Kakashi and then he connects with Obito. That thing is kamuied by Obito to the living beings world. He was in a world like Kakashi had been in when he was killed by Pein and where he met with his father. In that world, Obito's chakra hasn't gone yet and he somehow used kamui to trigger the meeting with Kakashi or the reason behind his capability of using kamui maybe that at the end he became a juubi jin for some time, let him give some sage art.
Btw, I do wonder whether Obito got blind or not!

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