Why was it important for the nations to acknowledge the return of our unique relationship with Hashem following the sin of the eigel?

Yehoshua sends two spies, Kaleiv and Pinchas, to investigate Yericho, and they meet Rachav, who in turn saves them from the officers of the king of Yericho, they form a pact with her, eventually returning to Yehoshua with a report of the terror the inhabitants of Canaan have of the Jews.

The people who were granted the supernatural knowledge to build the Mishkan were unique in having developed a specific prerequisite, yiras shamayim.

Hashem strengthens the new leader Yehoshua, the shotrim direct the people about 3 days time crossing the yarden, Yehoshua reminds 2.5 tribes about their agreement

Shemot Rabba 48:3,4- Chazal illustrate the special lineage of Betzalel and how it contributed to his wonderful qualities

Jews fight and defend themselves and the festival is established for future history

Gemara Megilla 12b, Esther Rabba 4:12- seemingly contradictory statements of Chazal revolving around the first letters of Haman teach us a lesson in the relationship between spouses.

The second party turns the tides, Haman is hung and Mordechai is elevated, counteractive letters are sent supporting the Jews and nations become fearful of them

3 controversial actions performed/paskened by Rebbi

The mitzva of "simcha" is best achieved through gladdening those who need the extra support.