Why does Trump think that raising tariffs reduces inflation?

He thinks that the other countries will be paying the tariffs. He is wrong, of course – the cost is paid by the US companies that are buying from overseas. And they pass the additional cost along to us.

Trymp sees this as a power play and show of strength.

His knowledge of economics is lower than zero.

Because he’s stupid and no matter how many times it’s explained to him he still won’t understand. Plus there is some one behind him insisting it’s a good idea…for unknown and scary reasons.
Other countries are just laughing.

Your question presumes that Trump believes that raising tariffs reduces inflation. It’s entirely possible that he’s lying. If does believe tariffs will reduce inflation, it’s because he’s a total fucking moron.

He doesn’t. He thinks other countries are the enemy and raising tariffs is an attack on the enemy. If Americans get harmed as a result then so be it, that is the cost of war sometimes.