Not thousands, millions - manufacturing jobs in America have fallen by more three quarters over the past 80 years because it's cheap and easy for American companies to outsource to developing nations that don't have worker protection. When they do bring manufacturing back, it's because it's cheaper and easier to automate than it is to train and use foreign workers.
That said, yes - I understand how tariffs are supposed to work, but what you're missing is that they're a small part of a much larger strategy he simply didn't have. In order to create jobs, the tariffs have to bridge the delta between more expensive domestic production and importation of foreign-produced goods, but Trump's haphazard implementation was done while we lacked capital, capacity, and foresight to start produce necessary items - so it just became an arbitrary tax on foreign goods.
And of course, we also need to consider the damage those tariffs did as part of the bigger picture, because the nations he slapped them on retaliated in kind, and that needless trade war destroyed foreign demand for American produce, manufactured goods, and services abroad, which our small businesses relied on.