Nehemiah 7 & 8 -The people were weeping when they heard the Words of Torah, then they rejoiced. Why?

Neh 8:9
Then Nehemiah, who was the governor, and Ezra the priest and scribe, and the Levites who taught the people said to all the people, "This day is holy to the LORD your God; do not mourn or weep." For all the people were weeping when they heard the words of the law.

The people were weeping when they heard the Words of Torah. While it would have been appropriate for the people to weep ten days later, it was not appropriate on the Feast of Trumpets. It is a celebration.

Neh 8:10
Then he said to them, "Go, eat of the fat, drink of the sweet, and send portions to him who has nothing prepared; for this day is holy to our Lord. Do not be grieved, for the joy of the LORD is your strength."

The people sorrowed because they had not obeyed Torah. Nehemiah told them to rejoice that they could now understand it and obey it. He told them to send food and drink to those who were poor and unable to prepare anything themselves. He wanted all the people to have joy in understanding Torah.