Speculation on why the Senju clan disappeared.

I've been recently interested in exploring the timeline of Naruto, and have come up with my own speculation on why the Senju clan disappeared from the story; They were wiped out by Madara Uchiha himself.

Setting the year of Naruto's birth alongside the main cast as the year 1000 would set the founding of Konohagakure as the year 935, approximately 65 years prior. (77 years prior to the start of the story.)

It is believed that both Hashirama Senju and Mito Uzumaki are 25 years old at the time. Sometime around the year 941 their child (probably a son) is born as this would be the parent (father) of the future Tsunade Senju. It is learned from the experience of this child-birth that the seal on the Nine-Tails is weakened, and probably the reason for them only conceiving one child.

It is also known that Hashirama fights a combo of both Madara Uchiha and the Nine-Tails at the Valley of the End during the year 965, or 55 years prior. This would mean that Madara Uchiha attacked Konoha and extracted the Nine-Tails from Mito Uzumaki.

Based on the location of the fight, I speculate that Hashirama was in Iwagakure for peace negotiations and was met by Madara in the Valley of the End during his rush to return to Konoha upon hearing about Madara's attack. During this time the Senju clan is wiped out by Madara who, as we know, hates them because of their dominance within the village / suppression of the Uchiha clan.

Hashirama beats Madara. Nine-Tails is resealed into Mito who somehow survived. Tsunade and her mother (who is pregnant with Nawaki Senju at this time) also escapes. And, in the same year 965, Hashirama dies either due to the injuries and over-regeneration from the battle or possibly because of the heart break from his clan being destroyed.