You lived 2000 years go? If you read the New Testament, you'll find the sects were fixated on Temple behavior. They were selling sacrifices in the courtyard of the Temple. Who could enter the Holy of Holies? Ironically, the only people who could dare to enter therein were the Chief Priest and the Roman soldiers who sacked Jerusalem. After the Temple was destroyed, the new Christians were able to find converts among the Jews who previously believed the Temple was invunerable. They were saying "See, God didn't protect the Temple".
If you build another Temple, someone else will come along and destroy it. Temples are the work of man.
The sects that you refer to were the non-religious and anti-religious groups, who had control of the political offices in the Temple, such as the high-priesthood. However the common people who revered and worshiped in the the temple were the religious Jews who followed the teachings of the Rabbis. The non-religious groups disappeared, they had no long-term staying power and were not interested in keeping up a Jewish facade when there was no longer any power positions for them to occupy. As for your remark about the third temple, it will be built by God after the coming of the Messiah, so it will have God's permanent protection.
The "new testament," of course, has about as much credibility as the koran.
The Third Temple will be forever. Read what you would call the Old Testament, and in particular the Prophets. If you want to make sure that you are reading the documents in question - all of them and only them - then I'd suggest browsing a copy of the Tanach published by a company called Artscroll. It'll have some things not found in the King James version, and lack others.
Those who converted had a very weak faith (as is the case with all converts of any religion, unless they had a sword to their throat or a gun to their head, as the ROP people tend to do). If they had read their Bible and heeded the warning that Moses gave toward the end of Deuteronomy, they'd have known that if they strayed from G-d's commandments that G-d would withdraw his special protection over the Land of Israel, meaning that the nation would be subject to the normal laws of history. The promise to the Jewish People would remain - in memory of the faith of our ancestors Abraham, Isaac and Jacob, and of the faith of those at Mt. Sinai - but it would postpone the coming of the Moschiach (Messiah) for a long while, until our behavior as a people was rectified.