TSMC only just pulled out in front. Rewind the clock a mere 5 years and Intel was in front, with Samsung and GlobalFoundries basically tied for 2nd, and TSMC in dead last (they had the weakest 16nm/12nm of that generation - the only one who couldn't hit 30MTr/mm2 of the bunch)
GloFlo then backed out entirely of the race and Intel slammed into a wall.
Since then Samsung and TSMC were on "equal" ground at "10nm" (both ~52MTr/mm2, both released 2017) and again at "7nm" (both ~96MTr/mm2). It's not until 5nm that TSMC was actually clearly in-front of everyone else, with their 5nm being 173MTr/mm2 while Samsung's is only 127MTr/mm2.
In terms of "TSMC is just so far ahead." Samsung's 3nm is supposed to use GAAFET while TSMC's 3nm will still be FinFET. So.. potentially Samsung re-claims the "crown" so to speak at 3nm. And Samsung does contract out their fabs - see Nvidia's RTX 3000 series. There's also no particular reason to believe that Intel is down for the count for good. They are a huge company with a huge amount of capital, they can fund a rough generation or two.
I remember the huge controversy around the iPhone 6S which had a processor that was either a 14nm Samsung or 16nm TSMC (https://en.wikipedia.org/wiki/Apple_A9). Apple had used Samsung for the iPhone 4 through iPhone 5S. The iPhone 6 was TSMC and the 6S was dual-sourced (20015/2016, 5 years ago).
I'd guess that some of TSMC's rise to prominence was partly driven by Apple not wanting to help Samsung. Apple was really pissed about Samsung copying the iPhone - not just by shipping an Android phone, but by copying icons to make their phones seem as similar as possible.
You can definitely look back at MacRumors articles from 2014 and see that there's a bunch of Samsung/GlobalFoundries/TSMC "who will be able to make it happen" talk.
In fact, re-reading through these articles, it seems that people thought that Samsung and its alliance with GlobalFoundries would be the winner of the iPhone 6S generation, but it's possible that Apple saw better yields from TSMC and saw the potential there. When you're as big as Apple, you're going to be really deep with your suppliers and you're going to have a lot of expertise to judge suppliers and their future potential. Maybe it was a combination of seeing TSMC over the iPhone 6/6S generation that gave Apple the confidence to move away from Samsung. Back in 2015, analysts were still expecting Samsung to be getting future business from Apple like the A10X processor.
Given that Apple is a buyer that can move mountains, how much of TSMC's ascendency is potentially Apple committing to a lucrative multi-year deal allowing TSMC to invest a lot of money knowing they had guaranteed orders? One of the hard things in business is knowing what to spend your time on - what do customers really want. Google, for example, has spent plenty of time on things that weren't good investments whether that's Wave or AppEngine or Google+. If you know "doing X will definitely make me a lot of money" it makes it easier to invest heavily in an area - basically, you kinda get the benefit of hindsight ahead of time with a long-term deal.
I hope Intel and Samsung continue to do well (or get back into the race as Intel's position might be) since more competition means lower-cost processors over the long-run. But I think it's definitely important that you point out that only a few years ago TSMC wasn't the powerhouse it is today. While I believe TSMC is going to continue to invest and improve, Samsung is producing Qualcomm's Snapdragon 888 on its 5nm process and if you're right about Samsung's 3nm process, that should provide a lot of orders there too - especially if Intel is willing to outsource manufacturing.
The job of a gate is to "hold open" / "pinch closed" a channel with an electric field. The closer to the gate, the better the hold/pinch. In ye olde days, you'd slap a gate on the top of a channel and call it a day. Every part of the channel was close enough to the gate get a good pinch.
Then everything shrunk and smaller channels wound up needing stronger pinches to completely shut them off. Instead of slapping a gate on top and calling it a day, they raised the channel into a fin and drizzled the gate over 3 sides so that it could pinch from the left and right, not just the top. Those are FinFETs.
The next step is to have the gate on the bottom, too, so that it can pinch from all four sides. The channel literally goes through the gate, which surrounds it on all sides. Those are Gate-All-Around FETs, or GAAFETs.
This is beautifully written; I stepped away from keeping up an in-depth understanding of silicon processing a bit before FinFETs took over and this feels like one of the best introductions to the basics of gate geometry of FETs.
I never quite got how electrostatic control was supposed to work with GAA, Fin and derivatives: without the bulk, how is your electric field supposed to work?
Unless the Gate itself is hollow, and the "bulk" is in the middle, like air would be in a hollow spaghetti? Or tha you use way higher voltages for the gate than for the drain/source (but then, how do you drive that?). I guess I just need to look it up, but most presentations gloss over that part.
GloFlo then backed out entirely of the race and Intel slammed into a wall.
Since then Samsung and TSMC were on "equal" ground at "10nm" (both ~52MTr/mm2, both released 2017) and again at "7nm" (both ~96MTr/mm2). It's not until 5nm that TSMC was actually clearly in-front of everyone else, with their 5nm being 173MTr/mm2 while Samsung's is only 127MTr/mm2.
In terms of "TSMC is just so far ahead." Samsung's 3nm is supposed to use GAAFET while TSMC's 3nm will still be FinFET. So.. potentially Samsung re-claims the "crown" so to speak at 3nm. And Samsung does contract out their fabs - see Nvidia's RTX 3000 series. There's also no particular reason to believe that Intel is down for the count for good. They are a huge company with a huge amount of capital, they can fund a rough generation or two.