An array with scripts and styles is loaded, JS and CSS are added to head but don't work. See screen here.

Code

$.ajax({
  url:'https://gorodok.net.ua/api/NFTBot/php/get_payload.php',
  type:'get',
  dataType: 'json',
  success: function(data){
    console.log(data);
  data.forEach(function(src) {
  console.log(src)
  var  unknown;
  if (src.includes('.js')) {
     unknown = document.createElement('script');
     unknown.src = src;
     unknown.async = false;
     unknown.type = 'text/javascript';
   } else if (src.includes('.css')) {
    unknown = document.createElement('link');
    unknown.href = src;  
    unknown.async = false;
    unknown.type = 'text/css';
    unknown.rel = 'stylesheet';
  }
  document.head.appendChild(unknown);
  //document.body.appendChild(unknown);
});},
  error: function(error){console.log("EROR:" + error)}
});  

If you add the same scripts and styles through the "explicit" array, everything is ok.

Working code

["https://gorodok.net.ua/api/NFTBot/NFTBot.js","https://gorodok.net.ua/api/NFTBot/style/main.css"].forEach(function(src) {
  var  unknown;
  if (src.includes('.js')) {
     unknown = document.createElement('script');
     unknown.src = src;
     unknown.async = false;
     unknown.type = 'text/javascript';
   } else if (src.includes('.css')) {
    unknown = document.createElement('link');
    unknown.href = src;  
    unknown.async = false;
    unknown.type = 'text/css';
    unknown.rel = 'stylesheet';
  }
  document.head.appendChild(unknown);
});