That's because you only have one element, and you keep moving it around, you have to create one element for each iteration
var grabWrapper = document.querySelector('.footerInfo');
var myArray = grabWrapper.children;
for ( var i = 0; i < myArray.length; i++ ) {
var pNewTag = document.createElement('p');
pNewTag.innerHTML = " this works ";
grabWrapper.children[i].appendChild(pNewTag);
}