Enums have been proposed for JS for quite a while (there was a sort of enum in "the lost version" ES4 and a TC-39 proposal stuck in Stage 0 for years now [1]). Enums have always had relatively simple JS output that resembles a somewhat common pattern in JS. It was a "standard", just never really a deeply adopted "standard".
What's today called "namespaces" in Typescript was originally called "modules" and then "inner modules" (to differentiate from "exterior modules") and is a tiny simplification on a JS pattern that was extremely common at the time of Typescript's inception called at the time "IIFE modules". "namespace" is a very C# name chosen in desperation (when it became clear that "exterior modules" were the present not just the future of the language and "interior modules" was too confusing a term to live), but it's a very old (and used to be extremely common) JS pattern that TS gave a tiny bit of syntax sugar to. It was a "standard" that existed at the time that was (rightfully) killed by AMD/UMD/CommonJS/ESM, but it is hard to fault the Typescript team at the early 0.x days thinking the "Stage Wild" JS pattern would possibly live on for many years to come. (This is also relevant to the patch notes for Typescript 5.0 as 5.0 is the first version [!] to itself be written as [proper/"exterior"] modules rather than namespaces. There are some interesting stories, including in these release notes for why that took so long to transition and what the performance benefits have been post-transition.)
Even those things that didn't seem like ES standards have some history as JS "standards". It's not like TS 0.x/1.x didn't support "standards", it is more that the TS team mostly decided to focus more on later stage ES standards (more likely to be accepted by browsers) rather than trying to "prollyfill" Stage 0 and "Stage Wild" standards.
[1] https://github.com/rbuckton/proposal-enum