Is the entire Torah of the Seventy-Years based on Shimon ben Shetach?

"Dathaniah is the story of King Benai, who went to Kochalit in the desert and captured sixty spies there. On his return, he was very happy and called all the wise men of Israel. He said to them, "Our ancestors used to eat salted meat while they were busy building the Temple. We too will eat salted meat in memory of our ancestors. They placed salted meat on gold tables and ate. There was a man there, a wicked and wicked man, named Eleazar son of Peorah. Eleazar son of Peorah said to King Benai, "The heart of the Pharisees is against you. What should I do? Raise up for them the thorn that is between your eyes. Raise up for them the thorn that is between your eyes. There was an old man there, named Judah son of Geddijah. Judah son of Geddijah said to King Benai, "The crown of royalty is too great for you. Put the crown of priesthood on the descendants of Aaron, who used to say, 'His mother was killed in the Midianites.'" And the matter was sought for and it was not found. The wise men of Israel divided it in anger. Eleazar son of Peorah said to King Benai, "The common man in Israel is like this, and you are a king and a high priest. Such is your law. And what shall I do? "I will do if you listen to my advice. I will trample on the Torah, what will be on it? It is bound and placed in a corner. Anyone who wants to learn, let him come and learn," said Rav Nachman bar Yitzchak. "Heresy was immediately thrown into it, and it was like a mimra. The written Torah was placed in the oral Torah, but from that moment evil sprang up by Eleazar ben Puira. All the wise men of Israel were killed, and the world was astonished until Shimon ben Shetach came and restored the Torah to its old form." (Kiddushin 60)

King Yannai killed all the sages of Israel except Shimon ben Shetach, who was Yannai's brother-in-law (Rashi) and his sister (Queen Shlomzion, as I understand it) who hid him.
It follows from this that the entire oral Torah tradition is based on only one person – Shimon ben Shetach!
And another question that arises from this, at the beginning of Tractate Avot, in the detail of the period of the couples, it is written that Shemaiah and Avtalion received from Shimon ben Shetach and Yehuda ben Tabai. If they received before Shinai killed all the sages, how was it that Shemaiah and Avtalion were not killed with the rest of the sages? And if they received after, how did they receive from Yehuda ben Tabai, who was a sage and was killed with all the rest of the sages?
Cheers!
Lavie