> aren't most languages designed and controlled by some relatively centralized organization, whether a company or a nonprofit?

This is a relatively recent development in programming languages. For example, your next sentence:

> Javascript, on the other hand, is a loose standard that different companies kinda sorta adhere to.

This could also describe the history of C. For example, let's look at the rationale document for the first standardization of C: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n802.pdf

I apologize in advance for quoting at length, but I could not decide what should be cut.

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The X3J11 Committee represents a cross-section of the C community: it consists of about fifty active
members representing hardware manufacturers, vendors of compilers and other software development
10 tools, software designers, consultants, academics, authors, applications programmers, and others.

<snip>

The Committee’s overall goal was to develop a clear, consistent, and unambiguous Standard for the C programming language which codifies the common, existing definition of C and which promotes the portability of user programs across C language environments.

The X3J11 charter clearly mandates the Committee to codify common existing practice. The Committee has held fast to precedent wherever this was clear and unambiguous. The vast majority of the language defined by the Standard is precisely the same as is defined in Appendix A of The C Programming Language by Brian Kernighan and Dennis Ritchie, and as is implemented in almost all C translators. (This document is hereinafter referred to as K&R.)

K&R is not the only source of “existing practice.” Much work has been done over the years to improve the C language by addressing its weaknesses. The Committee has formalized enhancements of proven value which have become part of the various dialects of C. Existing practice, however, has not always been consistent. Various dialects of C have approached problems in different and sometimes diametrically opposed ways. This divergence has happened for several reasons. First, K&R, which has served as the language specification for almost all C translators, is imprecise in some areas (thereby allowing divergent interpretations), and it does not address some issues (such as a complete specification of a library) important for code portability. Second, as the language has matured over the years, various extensions have been added in different dialects to address limitations and weaknesses of the language; these extensions have not been
consistent across dialects.

One of the Committee's goals was to consider such areas of divergence and to establish a set of clear, unambiguous rules consistent with the rest of the language. This effort included the consideration of extensions made in various C dialects, the specification of a complete set of required library functions, and the development of a complete, correct syntax for C.

The work of the Committee was in large part a balancing act. The Committee has tried to improve portability while retaining the definition of certain features of C as machine-dependent. It attempted to incorporate valuable new ideas without disrupting the basic structure and fabric of the language. It tried to develop a clear and consistent language without invalidating existing programs. All of the goals were important and each decision was weighed in the light of sometimes contradictory requirements in an attempt to reach a workable compromise.

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In general, standards that follow this path, codifying existing practice, that serve to coordinate interest between various actors, tend to work better than specifications that are written up-front and then followed by implementation. You can see this operating in a smaller way within current standards bodies and organizations, as you yourself alluded to with "relatively centralized."

> Javascript became the lowest common denominator, winning out not because it was better than say Java or ActiveX or Flash or whatever. It was just commonly available.

This statement is shockingly similar to what people say about C, as opposed to various other languages that were in the same space around the same time.