Rojo, I think the more interesting question is “Why weren’t spikes like this sooner?”
The DragonFlys aren’t really anything special when you actually think about. They are basically made out of the same material spikes have always been made out of (Pebax plate.. and really the pebax doesn’t matter; you can use almost any rigid, lightweight material, like carbon fiber obviously).
Shoes are really just a balance of weight, rigidity while still allowing proper movement, and optimal cushion to reduce impact/fatigue. More cushion usually equals heavier weight and reduced rigidity resulting in less pure speed (obviously sprinters would never wear something like Vaporflys).
So you make a full length plate for rigidity, and then pair it with a small layer of lightweight foam. The foam doesn’t actually make you faster; it actually slows you down- all else equal. If you exert the exact same amount of force in a shoe with a lot of foam, you’ll go slower than a super stiff rigid shoe with no foam. BUT the foam reduces fatigue over time, and the softer feel seems to tell the brain it’s okay to produce a lot of force and not get hurt. For distance running (especially 5k and up) this ‘cushion’ becomes more important and seems to overrride any max speed loss. Also, it probably helps some runners more than others. People that grew up running barefoot may not need much cushion (if any) to reduce fatigue for a 1500-10k. I’d guess ‘Western’ runners, especially those on the heavier side, benefit more from the cushioned shoes, but I’ll admit that’s mostly speculative. So maybe that’s why you’re seeing an increased ‘depth’ in lots of events, but not necessarily the same degree of faster absolute best times for the 1500 and 5k. (For the 10k though, it seems the cushion is helping pretty much everyone.)
So all shoes are simply trying to find the optimal balance of rigidity vs cushion while being as light as possible (and of course they need the optimal shape, but that shouldn’t be that hard to figure out these days).
So the question is: Why did it take so long for shoes like this to come out? How did no one think “Hey, let’s add a sliver of lightweight foam to provide some cushioning for the distance runners; with a full length plate, the shoe will still be pretty stiff, so maybe it could work?” Part of it, is that the foam just wasn’t as good before. With heavier foam giving less energy return, the trade-off of using foam was likely too high. With these newer, lightweight foams with energy returns in the mid to high 80’s, there’s not as much of a drawback (loss in speed) with foam, so you can simply reap the benefits.
Still though, the whole spike thing has been weird to follow. It’s really a very basic concept when you think about it, yet the running world is so amazed. And this is in the middle of a crazy technological world where we’re literally going to Mars and are close to interfacing with computers with our brains (NueraLink). So adding some foam to a stiff plate seems like a 1st grade project comparatively. I’m not trying to discredit shoe designers and the innovation of it, but I think it’s a pretty fascinating story. Maybe you should talk to more shoe designers about how they missed this for so long and what gave them the epiphany.