The 'sparsely populated America' has very deep roots.

Linguists call a language dead when there are no native speakers. People may speak it, but they learn it as a second language, often from texts, or from people who learned from texts. It ceases to change or adapt as a living language does.

Quipu have nothing to do with Maya.

Maya glyphs are a full language, capable of replicating the sound of any word in the language phonetically. Those thousands of codices were almost certainly similar to the written records of every other civilization: myths, histories, genealogies, administrative records.

What? No. He was working off photographs. I don't think he ever saw a glyph in person until after he published his research.

He almost lost his own work in a fire, iirc.

Honestly, what Landa left was pretty rudimentary, and early attempts to use it ended in disaster. It didn't seem to work. It was less ignored and more prematurely dismissed.

I mean, language decipherment is always a study in cognitive biases, and Maya is no exception. If anything, the tendency to ignore Knorosov because of Cold War political issues seems more frustrating in retrospect.

Various Mayan languages are spoken by millions of people today.

As far as reading Mayan, it started the process of figuring it out. It was a first step, not the whole.

There were reasons that made it a lot trickier than that. Among other things, written Maya uses multiple symbols to represent the same sound (think soft c and s in English, but many more variations) and scribes would freely substitute as they wrote. There was also very few texts to work from: most of them are on stones in the middle of jungles, and reproductions and photographs often left out details that were critical. And they thought it was written by people who spoke a form of Yucatec Maya, and it was a form of Ch'olti', which is a different language.

Deciphering Maya was a hell of an achievement. Truly astounding. Ot wasn't just a bunch of people being stupid until one dude was like "hey, what about this?"

He was brilliant and made a huge breakthrough, but the narrative that he did this "single handedly" really minimizes the work of the generation of epigraphers who took his insights and actually figured out how to read Maya.