What happened in R' Chananya's penthouse (18 Dvarim)?

Question

Speaking of Beyt Shamai, Yerushalmi Shabbat 9a also here:

Background:

"ואלו הן ההלכות שאמרו בעליית חנניה בן חזקיה בן גרון
שעלו לבקרו ונמנו ורבו ב"ש על ב"ה
ושמנה עשר דברים גזרו בו ביום:"

These are the halachos that were taught in the attic of Chaninah ben Chizkiya ben Garon: When they went up to visit him and voted, Beis Shamay held the majority over Beis Hillel. Eighteen decrees were enacted on that very day.

Action:

"אותו היום היה קשה לישראל כיום שנעשה בו העגל.
רבי אליעזר אומר בו ביום גדשו את הסאה.
רבי יהושע אומר בו ביום מחקו אותה.
...
תנא ר' יהושע אונייא תלמידי ב"ש עמדו להן מלמטה והיו הורגין בתלמידי ב"ה.
תני ששה מהן עלו והשאר עמדו עליהן בחרבות וברמחים.
תני שמונה עשרה דבר גזרו ובשמונה עשרה רבו."

That day was as difficult for Israel as the day the Golden Calf was made. Rebi Eliezer says, on that day they overfilled the measure. Rebi Yehoshua says, on that day they emptied it.

It was taught: R. Yehoshua taught, "The students of Beis Shamai stood bellow and were killing the students of Beis Hillel." It was taught: Six of them went up and the rest stood over them with swords and spears. It was taught: Eighteen decrees were enacted on that day....

Please explain what was going on in that penthouse and how those 18 regulations were ruled. Is that the accepted way of resolving Halochos, forcing the other side into the minority?

Answer 1

According to this article:

The Korban HaEida explains that the students of Shamai stood outside the house and prevented most of the students of Hillel from entering in order to sway the halacha.

Rambam (Pirush Hamishnah) says that all of the leaders of the generation were there, and there was no one fit to rule that was not present. Yet, because most of the sages in that place were from Beis Shamai the halacha was decided like Beis Shamai, who were the majority.

The Chasam Sofer (on Shabbos 17a) explains that although Beis Hillel was the majority, the students of Beis Shamai compelled them to rule their way through arguments. Some of the students of Hillel wanted leave to prevent a ruling, but the some of the students of Shamai stood at the door and did not allow the students of Hillel to leave. Meanwhile, six of the great sages of Beis Shamai went up and convinced the assembled with their arguments to rule like them.

(Added to address OP's comment:)

My understanding of this: The Golden Calf was made due to the fear and void created when they thought Moshe was not going to return. In a similar way, this event was in response to the Roman persecution and leaders of Beis Shamai felt that it was imperative to make decrees distancing the Jews from the Romans to preserve the Jewish People. As is often the case, during desperate times people that otherwise would not agree, go along with desperate measures. And so some of Beis Hillel went along with the decrees.

Answer 2

Adapted from Rav Samson Raphael Hirsch’s explanation (Collected Writings, §VII, “Rabban Gamliel and His Times”, pp. 84–90), who points out that Bavli Shabbos 17a is referring to the same incident:

For various reasons, Beis Hillel was avoiding a binding vote of the Sanhedrin (which was meeting in Chaninah ben Chizkiya ben Garon’s upper-floor study while he was compiling a commentary on the Book of Yechezkel/Ezekiel).

One day, Beis Shammai staged a coup. They came armed and basically said, “Nobody’s leaving until we vote.” The entire Beis Shammai stood guard downstairs with swords and spears, sending up just six of their membership to carry on the debate.

… they stuck a sword in the study hall, and they said: One who seeks to enter the study hall, let him enter, and one who seeks to leave may not leave, so that all of the Sages will be assembled to determine the halakha. That day Hillel was bowed and was sitting before Shammai like one of the students.

And those six almost persuaded the rest. Beis Shammai tended to appeal to the sharper scholars, and they began with the more persuasive arguments. And though Beis Hillel won in general (see elsewhere on this site for why that was), in the case of eighteen disputes and eighteen enactments Beis Shammai persuaded a majority of the Sanhedrin of their correctness. (Recall that only six of Beis Shammai were partipating in the debate and vote; the rest were downstairs standing guard.)

And those eighteen enactments, the Talmud says, (Jerusalem Talmud Shabbat 11a):

הא בתוך שמונה עשרה אפילו גדול אינו מבטל מפני שעמדה להן בנפשותיהן.‏
… even a greater court may not annul them, because [Beis Shammai] risked their lives for them.