1. it became much better at war than the others [0]
2. it became much richer than the others [1]
Much has been written about how Western values and/or institutions and/or any other causes led to 1 and/or 2 and the interplay between 1 and 2.
The warfare advantage is primarily tech-based against peer enemies. Training and sheer size may matter against asymmetric foes but against China it's basically whoever has the best technology.
Given the relative size of Western countries and the rest of the world (China is about four times as big as the US for instance), the West needs to be many times richer per capita to be a larger economic power than China or India. Note that the West used to be a much higher percentage of the world population in the past.
There's a lot of catching up both in technology in particular, including military technologies, and economic catch up more broadly; it is very unlikely that the West can leap again and grow/innovate so much faster than China & India can't catch up enough to dominate.
People in this thread seems to be too focused on what they see as a cultural decline within the US and not see the economic and technology long term catch up.
[0] see for instance https://press.princeton.edu/books/hardcover/9780691139708/wh...
[1] see for instance https://press.princeton.edu/books/paperback/9780691090108/th...