Why puppeteer blocks callbacks from execution?

This code as it is opens the browser and read a txt file line by line:

line 1
line 2       
line 3       
Stream closed

The thing I don't understand is why placing const browser = await puppeteer.launch(...) before const stream = readline.createInterface(...) blocks the execution of the callbacks in stream.on(...), the brower get launched but the console doesn't display anything.

const fs = require("fs");
const readline = require("readline");
const puppeteer = require("puppeteer");

(async () => {
  const filePath = "largefile.txt";
  if (!fs.existsSync(filePath)) {
    console.error(`File ${filePath} does not exist!`);
    return;
  }

  const browser = await puppeteer.launch({ headless: false, slowMo: 50, devtools: true });

  const stream = readline.createInterface({
    input: fs.createReadStream(filePath),
    output: process.stdout,
    terminal: false,
  });

  //const browser = await puppeteer.launch({ headless: false, slowMo: 50, devtools: true });
 
  stream.on("line", async (line) => {
    console.log(line);
  
  });
  stream.on("close", () => {
    console.log("Stream closed");
    
  });
  stream.on("error", (err) => {
    console.error("Stream error:", err);
  });
})();