How is the Klingon Empire so ridiculously powerful?

This is a bit confusing. They are literally (at least since the first generations after Kahless) born and raised purely as warriors; they find a way to fight with any form of challenge or "displease" them, which makes commercial relations and economic agreements almost impossible (hell even the Ferengi don't trust them for business, THE FERENGI); they despise science; they don't like and don't care about investing heavily in anything other than ships and weapons; the great houses are always in internal disputes for the government of the empire and for a seat on the High Council... well, it's a lot of stuff.

So how is it that after all this, a race like this is still one of the most prosperous and powerful in the franchise? Every empire, no matter how brutal and authoritarian it may be, also depends on relations with other powers to sustain itself. But in almost any alternative pre-26th Century scenario, the Klingons conquer vastly more successful and stable powers like the Federation and the Romulan Empire, which should be an impossibility since it's clear that the Empire is barely holding its own, and if it weren't for the Federation's help at Khitomer, they would have been practically wiped out after the destruction of Praxis.

I may have missed some important detail, so I'd appreciate your help, and I appreciate any feedback in advance.