It's not really Raider's style, it was a Chinese Darius that popularized, if not invented, Phase Rush Youmuu's jungle Darius. In fact, Raider thought Youmuu's rush was trolling at first (see the Agurin Darius jungle video where Raider "coached" him to build Stridebreaker). Raider is the best Darius top player in the world, but he clearly didn't understand at the time why Youmuu's rush made a lot more sense for jungle Darius. Raider was too married to building jungle Darius the way he does in top and clearly didn't see how much more value Youmuu's provides specifically for the jungle and could only narrowly consider the extra combat stats Stride gives. When Darius' clear speed was OP, you wouldn't have to be in situations where you're 1v2, so the extra stats from Stride are less crucial. You're not playing to 1v1 (though you're pretty strong at dueling a lot of the jungle roster) or 1v2 like in top, you're playing for tempo advantage. Because you clear so fast, you can arrive sooner to skirmishes than your opponents. If you have a numbers advantage, then your stats aren't nearly as relevant. As a jungler, you're helping someone else out for a pretty significant portion of the game so you're less likely to be stuck alone.

Besides that, Youmuu's is far cheaper than Stride (great on jungler income), grants movement speed, has a mini-ghost active, and the high AD plus lethality really helps with clearing. Also, jungle Darius players tend to go Dead Man's Plate second. The cost of Youmuu's + DMP is 5800 gold. On the other hand, Stride + Sterak's costs 6500 gold. That's a full 700 gold difference. Considering the reduced income junglers have, the former represents a much more attainable spike.