Gazza M it's always about power and control with this administration. the tariffs are a form of economic blackmail to bring the business world to heel in the short term.
Yep it's a racket. You've gotta think of him as an aspiring fascist leading a post-globalisation, partly deindustrialised economy. He has his brownshirts but he doesn't have decisive blocs of national capital as his allies, so he reasons he's got to try to carrot-and-stick a few countries or companies into subordination.
It will surely backfire badly even in that sense (it's guaranteed to do tons of economic damage). The way international power works, even brute measures such as tariffs, is too diffuse and complex for this. The stuff already circulating about secondary tariffs indicates a level of anxiety. Meanwhile a lot of the incumbent leaders whose countries he's targeting are gaining domestic support out of it.