There's a lot of great stuff at SemiAccurate throughout the years that details what went wrong at Intel and why. Unfortunately, you have to pay for it because Charlie has a practical stranglehold on semiconductor inside information.

And Charlie is a bit of a polarizing figure. He's gotten some things hilariously wrong, but he's also been dead on the money for a lot of issues, and his documentation of what's happening / happened at Intel is pretty much crystal clear.

You could probably browse through all the 10nm articles there and get a good idea of what happened without purchasing a subscription, if you have a decent knowledge of the semiconductor industry.

EDIT: If you read though these articles, even the parts that are available to non-registered users, a pretty clear picture starts to emerge - https://www.semiaccurate.com/tag/10nm/

I have yet to see an article with details about what went wrong in their fab process, but something seriously went wrong with their 10 nm fab process. Yields are low, many years in, and there were large delays.

This messed up their whole CPU development pipeline, because their designs are tightly bound to the process node, and it's a multi-year process. Because 10 nm hasn't ever worked in volume, and their new CPU designs are based around 10 nm, their latest server chips are still based on optimized Skylake microarchitecture, which was first released in 2015.

Early indications are that Intel's next process node (which they're calling 7nm) is also experiencing problems, if those problems aren't resolved, that probably means they'll have cpu designs for 7nm that they also can't ship in volume, in addition to the 10nm designs.

If they can figure out their fab issues, and they don't have a corporate implosion, I'm guessing they'll start making competitive CPUs again; they've been way behind before and come back (anti-competitive practices helped make sure they had the finances for that, of course).