Amazon details Project Kuiper satellite Internet

Good to see more competition entering the market, though I don't have high hopes for the service. They specifically avoided buying any launches from the cheapest launch provider (SpaceX) for political reasons so that's going to cost a lot more to put out the service and they're launching substantially fewer satellites so the available bandwidth is going to be lower than Starlink.

If it achieves any kind of popularity it will quickly reach the same problems Starlink has had in certain areas, likely even earlier given the fewer satellite count.

Will this be able to leverage the existing Starlink satellites, or does SpaceX need to deploy a whole other massive globe-encompassing fleet of redundant satellites?

No this is a competitor. Amazon has basically bought every other heavy lift rocket in the world for the next couple years.

The bought from ULA, all outstanding Atlas 5, Ariane 6 and BO New Glenn. And they will have to buy more.

Exciting news and a critical option to have re: national security specially given Musk erratic behavior these days.

SpaceX is a reliable national security partner. I'm not sure where this myth started that Elon/SpaceX is somehow an unreliable partner.