When did we REALLY accept the Torah?

Question

It is a known Gemara (https://www.sefaria.org/Shabbat.88a.5?lang=bi&with=Sheets&lang2=en) That the Jewish people "re-accepted" the Torah during the times of Esther.

Question 1. Why did the Jews of that time specifically merit to be the ones to re-accept the Torah? had there been no more deserving period of Jewish people prior to the story of Purim?

Question 2. In what way did they re-accept, did their practical observances change in any way?

Answer 1

Question 1. Why did the Jews of that time specifically merit to be the ones to re-accept the Torah? had there been no more deserving period of Jewish people prior to the story of Purim?

In the Maamar Ve'atah Tetzaveh, the Rebbe explains that every exile present challenges with regard to observance of the Torah and mitzvos. In the time of Haman, those challenges were great:

In the times of Achashverosh, by contrast, the Jews experienced the ultimate of descents. Every exile is associated with a veiling and concealment of G‑dliness. {For all exiles follow the paradigm of the Egyptian exile,28 of which it is written,29 “They did not listen to Moshe because of their dwindled spirits and hard toil.” Similarly, [all subsequent] exiles present several challenges with regard to [the observance of] the Torah and its mitzvos.} In particular, then (in the time of Haman), there was an even greater veiling and concealment [and the very lives of the Jewish people were endangered].

Never­theless, the thought of anything outside [the context of our faith], heaven forbid, did not occur to them.)

Moreover, they exhibited self-sacrifice in the observance of the Torah and its mitzvos to the extent that they congregated to study Torah communally with self-sacrifice.}

It was Mordechai, the Moshe of the generation, who inspired this self-sacrifice. [On this basis, we can understand the verse] “The Jews accepted what they had already begun,” that the giving of the Torah was merely a beginning and their acceptance came at the time of Haman’s decree. For their actual expression of self-sacrifice in the observance of the Torah and its mitzvos elevated them (in this regard) to a level above that experienced at the giving of the Torah. Therefore, this was when the acceptance of the Torah took place, “the Jews accepted.”

Thus, the Jews were willing to sacrifice their life for their faith. As the Rebbe explains further in the maamar.

The Rebbe explains that for example, during the Chanukah-story, only a small part showed mesirus nefesh. However, during the Purim-story, the whole of the Jewish people showed mesiras nefesh and took upon theirselves to accept the Torah, even though it was very dangerous to do so at that time.

at the time of Haman’s decree, the entire Jewish people displayed mesirus nefesh

The Frierdiker Rebbe, the previous Rebbe, explains in the Maamar VeKibeil HaYehudim 5687 (1927) that:

In the time of exile, everyone is broken and crushed - but it is precisely at such a time that one reaches the [essence of the] luminary itself. This in turn allows us "to keep a constant light burning."

In the time of Purim, there was a huge ammount of mesirus nefesh, as the Midrash Rabbah in Esther Rabbah 9:4 says:

After he erected the gibbet, he went to Mordekhai and found that he was sitting in the study hall with the children sitting before him, with sackcloth on their waists, engaging in the study of Torah, and they were screaming and weeping. He counted them and found there twenty-two thousand children. He cast iron chains on them and deployed guards over them. He said: ‘Tomorrow, I will kill these children first and then I will hang Mordekhai.’ Their mothers were bringing them food and water and saying to them: ‘Our children, eat and drink before you die and don’t die hungry.’ Immediately, they placed their hands on their books and took an oath: ‘By the life of Mordekhai our master, we will not eat and drink, but will die while fasting.’ All of them began weeping loudly until their cries reached the heavens. The Holy One blessed be He heard the sound of their weeping approximately two hours into the night.

How would a person respond when someone treatens him with death if he studies further? The people did not stop studying Torah. No, they continued, accepting the risk. Why? Because the Torah was way more important than their lives. They wanted to live with G-d, no matter what!

The Etz Yosef in his commentary to this Midrash actually links the number of students to Matan Torah.

ושנים עשרים אלף תינוקות. [יש מדרשים אומרים שהכונה בשנים ועשרים אלף תינוקות לשנים ועשרים אותיות באל"ף בי"ת ורצה לבטל את מרדכי ותלמידיו מלעסוק בתורה (יפה ענף ועץ יוסף מהדורא קמא)]. ולי נראה שקבץ כמספר הזה שיעסקו בתורה כנגד המלאכים שבאו עם הקב"ה להר סיני בנתינת התורה לישראל כדכתיב רכב אלהים רבותים אלפי שנאן אדני בם סיני בקדש. וקיבץ תינוקות סך הנ"ל משום שיהיה הבל פה שאין בו חטא כלל:

This whole question could also be linked to the question whether Matan Torah was out of coercion or out of love. See my question here, with fascinating answers. The Tosfos on that famous Gemara says:

But at the time of Achashverosh, they accepted [it] with their consent from love of the miracle.

See similary, the commentary of the Ohev Yisrael (Parashas Zachor and Purim), on the significance of "accepting out of love":

But even so, they accepted it in the days of Achashveirosh, which was a time of great pain and distance from G-d, and even so, they accepted it upon their souls, even though they were in a very lowly state, and committed to do all that was written in the holy Torah. And so we find that there was no longer any mitigating claim about the acceptance of the Torah after they accepted it out of the desire of their hearts.

And, the Emes LiYaakov writes (אמת ליעקב - ברכות, זרעים, מועד):

שבאמת צריכים לשני הענינים, היינו העבודה מאהבה והעבודה מיראה - Sometimes we need worship out of love and also out of fear

I hope this answers your first question.