1. The US went from net-exporter to net-importer (so: reciprocal and cascading retaliation was not possible on nearly the same scale)
2. Durable goods deflated until they were a small part of the economy
That's why the reaction this time around was a "buy the dip" and not another great depression (although the great depression itself was exceptional, countries successfully wield protectionism all the time, see China). Unfortunately, tariffs are only one component of functional industrial policy. Imagine you are considering investing in a factory: you don't just need protected outputs, you need cheap inputs, available capital, and above all enough stability to reasonably expect to see your returns before one of those pillars gets yanked. Trump got halfway to step 1, so he inflicted most of the damage without even buying a reasonable chance of success. But yes, at least the damage was relatively small, although "he followed it up with Iran which was much worse" isn't much of a consolation.