My question is a bit long-winded so I'll summarize first:
TL;DR How did Mordechai rouse the will of all the Jews of Shushan to agree to fast for three days? And further, why did Esther limit her request that only the Jews of Shushan fast?
I look forward to the interesting answers. Thanks and happy Purim!
Part 1
It says in the Megilla, 4:15-16:
"Esther instructed a reply to Mordechai: "Go and assemble all the Jews found in Shushan and fast for me. Don't eat nor drink for three days, night and day..."
We can reasonably understand that not all the Jews were necessarily observant. (We know that the reason we were in the predicament that we were in was due to our overall behavior including some specific incidents such as attending Achashverosh's party.)
So, the notion that all of the Jews (even just those Jews living in Shushan) would decide to all agree to listen to Mordechai is hard to imagine. Maybe 50% or maybe even 80%, but not all the Jews in Shushan.
The simple answer might be that it was a miracle whereby everybody just wanted to do the right thing and agreed to listen to Mordechai and not eat for 3 days straight. Essentially suggesting that we lost our own willpower. If that's the case however, then how would the fast actually bring about the redemption like it seemed to do in the story of Purim? It wouldn't be on our own merit if Hashem suspended our free will.
Therefore, it seems that it must have been due to the people's own will to collectively take on this fast. The question is how could every Jew in the city of Shushan agree to do this? Not one Jew disagreed with Mordechai?!
I think this is very important because it seems the they key to forging Jewish unity is found in whatever approach Mordechai must have used to instantly rouse the Jewish people to fast. The Megilla doesn't really tell us what Mordechai did to rouse the collective will of all the Jews. It just says that "Mordechai went and did everything that Esther had instructed him".
Keep in mind, Mordechai only heard about the decree the night before (or the previous day) and Esther didn't even yet know about the decree until he told her through a messenger, so the people of Shushan may not have even realized the immediate threat (unless the news spread quickly, but even if it did it wouldn't necessarily be deemed "credible" by everybody).
Part 2
The second part of the question is why did Esther only requested that the Jews of Shushan fast? Sure, it was practical since it must have been hard to spread information over long distances in those days. However, the fast itself (for three whole days and nights) was impractical and yet the dire circumstances called for it. So, why limit it only to the Jews of Shushan?
That is my question. I have already read something which I think might be an answer, but I'm curious what everybody here has to say. Thanks for reading my long-winded question and happy Purim!