I'm less surprised about the fact that JS can be fast, and more that a vanilla trie can be fast and (hopefully) resource-efficient; I had the impression that any scalable index would need to compact the trie in some manner (i.e. combining multiple characters in one node) or do other algorithmic improvements that I don't know about. (That's why I looked at the code, to find those -- but I didn't really find any)
The current release of Lyra is treating the trie structure as a tree (of course), but we're planning to start approaching it as a graph for the exact reason you're mentioning. We don't have performance comparisons yet, but we'll document everything
