Haven't watched it, but have read and watched a lot of Lighthizer and other economists familiar with his thinking.
Basically, the rationale for tariffs is that the current US-sponsored system of trade is bad for American workers. We create artificially high levels of debt through a set of policies that encourages outsourcing of production, jobs, and supply to trading partners overseas, who complete transactions, create a supply of US dollars abroad, create more demand for dollars (which we print) through increased trade, and create more jobs abroad. Our trading partners then use US dollars to purchase US assets such as US real estate or shares in US companies.
Asset holders in the US (i.e. people with retirement accounts, real estate, and other possessions) manage to do okay because assets appreciate in value, but for people without assets, their wages stagnate while their living costs increase.
The thinking is that tariffs are needed to shock the global economy out of its current design and into a new system of smaller multilateral trade in which the US can use its levers of power to bring back production to the US and create more jobs and more supply.