According to Osho, Bhishma (and similar religious men) sided with Duryodhana not from confusion or complicity but from total surrender. A truly religious person has no personal will; he stands wherever life, the divine, places him—even amid darkness and certain defeat. Bhishma knew truth lay with the Pandavas, yet accepted the harder station, exemplifying supreme surrender; hence Krishna honored him.
They didn’t choose sides; they let God’s will place them, proving surrender by staying even on the hard, losing side.