One more optimization idea: instead of the trie mapping to the suffix string directly, then instead make an array of unique suffixes and let the trie map to the index into the array, e.g.
const suffixes = [",,,", "a,u,u,u", ",,i,s", ",,,s", "i,a,a,a", ...];
and then use the index of this list in the
var serializedInput = "{e:{n:{ein:0_r: ...