Before we go any further, a word about the term "Mashiach". It simply means "anointed", which can also be interpreted as "appointed". Kings and High Priests were usually  anointed with the holy oil described in Exodus 30. In some cases, balsam oil was substituted.  The kings are often referred to as "Mashiach Hashem" (the L-rd's anointed). Even the non-Jewish king, Cyrus the Great of Persia, is called "My Mashiach" (Isaiah 45:1), as he was appointed by G-d to have the Temple rebuilt. The future deliverer is sometimes referred to as Mashiach, but rarely so in Scripture. We  usually find him simply called "My Servant".
Now, why would Rabbi Akiva have been fooled to believe that Bar Kochba was the Mashiach? RAMBAM explains beautifully. No one is to believed to be the Mashiach until he accomplishes several tasks. He must restore Israel to its land, rebuild the Temple, free us from repression, and usher in world peace. Then, and only then, is he to be recognized as the Mashiach, We find nothing in either the Written or Oral Torahs about accepting him on Faith. However, RAMBAM posits that there is a preliminary stage. This is called "Hezkat Mashiach" (assumed to be Mashiach, until proven otherwise). That will be a king of the House of David, occupied with Torah like his father David, who fights the Wars of HaShem. But what is meant by "king"? Literally a king? A great military leader? Perhaps a great spiritual leader? And what is meant by "wars"? Literally? Or perhaps the great struggles against false ideologies, evil and corruption? Although most rabbis accept the idea of a "Mashiach ben Yosef" who will do the fighting, die in battle, and be immediately succeeded by Mashiach ben David, Maimonides rejects that idea. He sees it as two stages in the career of the same person; Mashiach ben David. If we see someone occupied with these battles, we may assume that he WILL BE the Mashiach. If, however, he goes away from G-d, or, simply dies without having accomplished the main tasks of the Mashiach, he assign him to the dung heaps of Jewish history. Therefore, Rabbi Akiva, seeing this valiant warrior, who kept the Romans on the run for several years, believed he was "Hezkat Mashiach", until he finally died. What all agree upon from this discussion is that no one can be regarded as Mashiach until he accomplishes his mission. We search in vain for any hint in Scripture to the contrary. Other than G-d, no one and nothing is to be accepted on Faith. On the contrary, Deuteronomy 13 warns against "prophets" or Miracle Workers" who seek to take us away from G-d and His commandments. The Torah says "why is he able to prophecy and do miracles? G-d is testing you".
What will be the nature of the Messianic Kingdom from a Torah perspective? Why do some believe that the founding of the State of Israel is the beginning of  that era? Why do some believe the opposite, while many fall in the middle? That will be my next post.