Also, if the Twelver says his final Imam is 'hidden', we would say that the Prophet (Salla Allahu Alayhi Wa Sallam) is alive in his grave and benefits the Muslims from beyond the veil of the unseen, it would be superfluous for Allah to place another Infallible who is not directly accessible while there is already one Infallible benefiting the Ummah in this manner.
Everyone can make this claim, but Quran shows after Abraham, Imammate was passed down his offspring and didn't stay with him.
Like wise this nation not only need this hidden guidance (Mohammad could of been the one to go ghayba and return) but they need a series of Guides and Successors who were among the people and who the people are tried with. This trial was a good trial on God and a grace just as it was always grace before.
God could of made Moses stay on earth and be the guide and go hidden, but it was not superfluous to appoint a series of leaders that guide by God's command, 12 Captains that ways to God and who people should not mix from drinking their place uncertain water and falsehood with their truth.
This has a wisdom, the number 12 has a wisdom, and Elijah going into hidding and then after Zakeriya and Yahya and Isa, being the one who takes this mantle of spiritual guidance also had a wisdom.
Jesus is to a play a role to come, but he being the spiritual guide on earth is not one of them, but as the hadiths show, he will return while the Imam is among us and pray behind Imam Mahdi.
There is a wisdom in all this, if I or a Shia cannot articulate, it doesn't make it go away.
Part of the wisdom is that first people are tried with real rope from God that is physically present, and see how they act towards God through them. Then when they are not present among us, see who mixes with their authority others and demolishes the whole foundation of God's door and submission with tainted leadership and unproven authority.
This is a trial that has been repeated. The boat in the waves when things get hard for some reason those on it become sincere and worship God sincerely. Then when they are brought to safety and reach the promise of God, they rebel like Bani-Israel began to rebel after Moses brought them to safety.
This cycle repeats itself but the Mahdi is a long trial, because the cycle this time must stop. This time people will come to the truth and the earth will be illuminated by God's light through Imam Mahdi.
This time we will have to wait to the extent that is a guarantee that when people are brought to safety they will not assoicate in the divine leadership which is linked to God's Kingship the likes of the Samiri etc, but rather submit to the clean pure stream and enter the door that God has opened for them.
There is wisdom in sealing revelations and in sealing the divinely appointed leaders, so, and keeping that guidance of Abraham on earth in a remanent of pure family from his offspring. It has wisdom.
The Quran elaborates on it, manifests it's beauty, and shows it. People will have to awaken to the arguments of the need of a chosen one from God and guidance that is tread by him, and the world will have to want justice and to be ruled by it.
The world will recognize the need of a ruler and authority from God. It's bound to happen, we pray to be of those who speed up the process that leads to that and not be of those who delay it.