The pitch was the same. But the condition of the pitch changes due to the dew at night. This happened because BCCI had to organize the Day/Night match due to their broadcaster's request for more TRP.
Australians were very good at reading the pitch. They have played a lot of cricket in India. They knew that the pitch was made up of black soil, which gave a good turn and bounce in the afternoon and became absolute rode under light and dew. This is the reason they have decided to bowl first in the final match.
I don't know why India chose this particular pitch for the final match and did not select the pitch which would help them in batting. Their batting was exceptional, and they should have made a batting pitch on the final day.
TRP generates revenue, and the money is what everyone is after. So, you can not blame BCCI for organising a day/ night match. Usually, the ICC tournament matches are Day/ Night because of the spectators' turnout.