Earlier quoted context omitted.
That is approximately the opposite of how it happened. Several different groups of people invented processes that worked for them (e.g., Scrum (1995), XP (1996), FDD (1997), DSDM (1994)). They all liked what they had done, but discovered they had commonalities that were worth talking about. They got together for a long weekend and came up with the Agile Manifesto (2001). Having lived through the transition, I promise…
You're not the only one who lived through the transition. And IME the good practices that are used in Agile processes mostly are the ones that were well-known and widely-used. People have written automated tests for decades. People have been testing at the interface level since the dawn of OO and before. Put those together and you've got what is now called unit tests. People have been making small changes to improve…
As to your assertion that everything good was in wide use before: that's not how I recall it. For example, CI: the Joel Test, written in 2000, suggests that the vast bulk of shops couldn't even manage to do a daily build, and he didn't even mention CI as an option. Also, it's not clear to me what a 13-year-old's imaginings proves about what a majority of development shops were doing in the mid 90s. My recollection is that waterfall was the majority, with most of the rest of the shops doing code-n-fix. And the first edition of McConnell's Rapid Development, which was a mid-90s book, either doesn't cover or treats as exotic most of the Agile notions.
But honestly, I don't know that it matters. I'm not sure why, but you seem eager to prove that there was nothing good about it based on your incorrect version of the history. The good news from your perspective is that what's sold as Agile has turned almost entirely into dismissable buzzwords, and as a fad I expect it will be extinct soon. There's nothing left to fight off.
But personally, I plan to keep using and evolving what I learned from it. If you want to see what a shop like that looks like (including all those practices you mention above), feel free to drop by in SF sometime. We like visitors.