Megaprojects explains the Belt and Road Initiative:
This is a rather comprehensive video explaining China's Belt and Road Initiative.
The BRI is the initiative of Xi Jinping, announced in 2013. Prior to that, China's guiding principle was from Deng Xiaoping: "Hide your Strength and Bide your time."
Apparently, when Xi took over, he decided that the time to hide your strength and bide your time was over; that China's time to shine has arrived; that China was ready to take to the stage as a world leader, and to displace the current world leader.