What conditions usually lead to a strong Dollar Index, and why is this beneficial to the US but not beneficial the rest of the world.

This week we will discuss the (DXY) a.k.a the US Dollar Index.
DXY — U.S. Dollar Index Chart — TradingViewLinks to an external site.
Part One –
Please research and familiarize yourself with the US Dollar Index.
Explain:
a) What is the US Dollar Index is,
b) What is it weighted against,
c) Why do we have it and why is it important,
Part Two –
1. What conditions usually lead to a strong Dollar Index, and why is this beneficial to the US but not beneficial the rest of the world.
2. What conditions usually lead to a weak Dollar Index, and why is this not beneficial to the US but is beneficial to the rest of the world.
Part Three –
“Excluding a major economic crisis”, why would it be important for the United States to prioritize a weak Dollar Index, even if it often leads to yearly trade deficits?