These are two entirely different scenarios. Imam al-Mahdi was not in charge of an entire community , nor the political leader of any region or location.
As expected, your answer would be "two different scenarios". However, how does the "diffrent scenario" your 12th imam lived in do not require anybody be a leader while he is away? What an irony since you claimed Prophet (saw) left Ali behind to lead "not-an-entire-community"* in Madinah while he (saw) was TEMPORARILY away.
*"Not-an-entire-community" since tens-of-thousands others followed Prophet (saw) to Tabuk.
You know what. Surely your 12th imam did not in charge of an entire community. But he certainly in-charged of his own followers. It was still a group that need someone to lead. Ironically, leaving behind his group with no leader is perfectly make sense from his perspective and in contrary to your claim about Prophet (saw).
The ones ruling were an oppressive regime, such that he and his follower were often shunned into secrecy out fear of being murdered.
Being in secrecy does not require a leader to lead the followers? Another logical fallacy here. By the way, do not say that the 12th Imam is the leader because he, in reality, does not lead.
Muhammed[saw] on the other hand, presided over an Ummah that was barely in its infancy, with external enemies waiting to attack, several hypocrite tribes in every region. He was the one people turned to for everything, and had far more power, influence and control over the Arabian Peninsula. If he were to pass away it would indeed have been an enormous power gap.
Unfortunately for you, history has shown that there was no power gap happened. Not more than 24 hours after the death of Prophet (saw), a leader was selected. And that leader (and the one after him) brought Islam to next level unparallel to the human history i.e. "steamrolling" the 2 superpowers of that time and brought Islam beyond to the world. Hence, your "hypothesis" with regard to so-called concerns of Prophet (saw) above is truly baseless and unfounded.
However, we do not find him -as per the Sunni view- stating that 'you choose amongst yourselves who your leader will be', nor appointing anyone himself. It was dead silence. For Imam al-Mahdi, after he appointed his representatives, he clearly stated no-one will be an official representative and that he is entering into the longer Ghaybah. He still remains the Imam of the time, mind, but circumstances are earth and sky between this, and what was the political scenario at the time of the Prophet [saw]. There was total silence [allegedly] on part of the Prophet [saw], but clear words from Imam Mahdi about the issue of succession.
Thank you, Sir. You are just refuting yourself here. The whole point of your argument in that article was that "it make more sense for a leader leaving his followers behind with somebody in-charged of them". You argued that the current leader should either:
1) pointed out who should be in charged; or
2) the least, tell his followers how to select a leader.
And by you to say that the mahdi "clearly stated no-one will be an official representative and that he is entering into the longer Ghaybah" shows it does make sense for a leader to leave behind his followers without anybody in-charged of them.
What an irony!
Just to add, we also made a note that even if you do not believe he should have appointed anyone, surely he would have made a reference to the people that they must choose amongst themselves? He does not have to appoint like the first Caliph did, but he can organise a Shurah like the second one had done. Even if you claim he did not want to set the terms for the Shurah, he could have at least declared he was passing away, and it was of utmost importance for the Muslims to engage in consultation, and that leadership must to go the Q'uraysh and only they must be made candidates for leadership. Yet again - there is nothing but silence.
Silence from Prophet (saw) was not ok but silence from 12th imam was ok, really?
I stress this point again. Prophet (saw) was silent but the ummah had a new leader in less than 24 hours. A proper leader who took Islam to the world and left nothing for himself. Whereas 12th Imam clearly stated no one should lead after him. No wonder Sunnis became a world power whereas Shias have to wait for Khumaini to wake them up from dream.
Note: We believe that Prophet (saw) did not totally silent with regard to leadership after him. He (saw) did give hints who should the ummah choose after him and that hint led to Abu Bakr.Please remember, your article was about logical argument on the premise that "it makes more sense for a leader having someone in-charged after him". Your 12th imam is an antithesis of your own argument.