How can I access a pages dataLayer using Chrome Extension Manifest V3?

Question

I have the below script running on my script.js file and everything runs as expected but it does not recognise the dataLayer variable?

chrome.tabs.query({ active: true, currentWindow: true }).then(function (tabs) {
  var activeTab = tabs[0];
  var activeTabId = activeTab.id;

  return chrome.scripting.executeScript({
      target: { tabId: activeTabId },
      func: function() {
          console.log(dataLayer);
          return JSON.stringify(dataLayer);
      },
  });
}).then(function(results) {
  var datalayer = JSON.parse(results[0].result);
  console.log(datalayer);
}).catch(function(error) {
  console.log('There was an error: \n' + error.message);
});

The result I get is:

Uncaught ReferenceError: dataLayer is not defined at <anonymous>:2:23 at <anonymous>:4:9 (anonymous) @ VM896:2 (anonymous) @ VM896:4

but when I type "dataLayer" into that windows console, it recognises it? Console Screenshot