To the original question
According the the BaH on Sotah 14a, Rabbi Hama son of Hanina says that Moses’ burial site was hidden because God knew he would eventually destroy the temple and exile Israel from the land. If they knew where Moses’ burial site was, they would go to it, alert Moses of the evil decree, ask him to pray for us, and Moses would nullify it.
He proves that Moses was unique in his decree-nullifying ability, citing the sin of the golden calf, and pointing out that of all the righteous people in the generation, Moses alone was approached by God to intervene.
He also remarks that the righteous are even more precious in death than in life, which would exacerbate Moses’ special role.