The first paragraph in the introduction claims the "failure to fulfill expectations" of Algol 68 and Ada were because they were designed by a committee. Leaving aside whether they were or weren't disappointments, neither was really designed by a committee. Algol 68 was famously presented as a fait accompli to the IFIP committee by Adriaan van Wijngaarden, as documented by Dijkstra and leading to the minority report and ultimately Wirth's Algol W and then Pascal. Ada was largely designed by Jean Ichbiah, and all the various committees of the US DoD did were choose his design over the competitors.

Both languages strongly appealed to me, probably because of their cohesive (one-man!) designs, although I never got the chance to use them professionally. So I do agree that a strong, usually one-person, design is the way to go. But both Algol 68 and Ada failed for other reasons. I'm speculating, but I suspect they simply required too much of the average programmer: mathematical sophistication in the case of Algol 68, and discipline in the case of Ada.

The other plank of TFA's argument is that successful languages are built up slowly based on experience of requirements. I think if such a language ends up any good, it's either luck or someone spending a lot of effort pushing back on bad proposals. I'm sure you too have a list of languages in mind which grew in an undisciplined manner, until they strangled themselves. I think of language designers who allow that as like Maxwell Smart in Control headquarters, running coloured strands of wool between pushpins on a map until it's a woolly mess.

I suspect what really made Lua a success is it found users among game developers at the right time in its development, and did not try to be much more than that. In that sense, by listening to users and adding things, they achieved a good design (I assume – I don't really know the language), and because it did not achieve wild success that constituency of users was not so diverse as to baroquify the language.

A language can fail if it is a clean design but doesn't have users (Eiffel). A language with an ugly, committee, design can succeed if it has users (C++).