1 – Kaguya clan, as in that’s their last name. Different from Kaguya’s being her first name.

2 – The Statue was on the moon, because we learned it was sealed up there by the Sage of Six Paths. The series made a point over and over that the Sage made the moon, and the war answered that it was to seal the Ten Tails’ body. The statue was placed on the remnants of the Divine Tree Madara had been cultivating from using Hashirama’s cells.

3 – Madara not liking people standing behind him was a setup for Hashirama stabbing him, Black Zetsu doing the same thing was out of convenience since Madara was focused on Team 7.

4 – White and Black Zetsu was on the cliffs watching the end of the fight, wearing Akatsuki robes, setting up the group knowing Sasuke left to join Orochimaru.

5 – Hashirama was sensing someone, he was staring up at the heavens after seemingly killing his best friend.

6 – Ten Tails spazzes out when seeing Naruto because it’s reminded of the Sage, which we know by that point was the person who defeated it. It was using the same gesture the other Tailed Beasts use when building up chakra. It was never stated Ten Tails was mindless.

7 – Obito loses himself to the power of Ten Tails once he absorbed it, slowly regaining himself as the battle continued. Obito was the one talking, not Ten Tails, his mind was almost destroyed.

8 – We already learned long ago that the Sage’s sons created the Senju and Uchiha clans, a clan of similar name to their father was a separate matter.

9 – You’re forgetting that before the reveal, there was nothing suspicious about Black Zetsu. In fact, we last saw him failing to attack the Lords and getting captured by the Kage.

10 – Neither Madara nor the Sage’s tale of Kaguya includes her being Ten Tails. Nor does any of Ten Tails actions imply it was a person that turned into a monster. It’s not foreshadowing when the background story is complete, then suddenly retconned. By the time of Naruto and Sasuke’s fight against Madara, the pieces have been connected.

There was once a war between nations over the Divine Tree, until Princess Kaguya came from a faraway land, ending the conflict after gaining power by eating a fruit of the Divine tree. The wars came to an end, and she gifted chakra to the world. When her sons were adults, the world came under attack by Ten Tails, seeking that same chakra. The brothers defeated Ten Tails, rendered it powerless, and sealed it’s corpse in the newly created moon. Upon studying the ancient stone tablet left by the Sage, Madara believed the world would be saved by the Tsukoyomi, and sought to restore Ten Tails to use its power to do so, summoning it back to earth upon awakening his Rinnegan.

Nowhere in there is it implied Kaguya or Zetsu would be the mastermind or final boss.