Delay loading of html5 video after the rest of the page finished loading

I have a video element being used as the background of a section towards the bottom of a page I'm building. I'm trying to build a sort of 'lazy-load' for it by storing the src as a data-src attribute and using jQuery to apply it to the src attribute after the other assets have loaded (since it's not a hero image or anything, I want to load a poster to save cut load-time and then load the video later). It doesn't seem to be working for me at all. The src attribute is applied correctly but the video doesn't load or autoplay. Am I approaching this from the wrong angle? Is there a better way to accomplish it?

Building on wordpress.

Basic HTML

<video width="100%" loop controls autoplay class="connect-bg"><source data-src="<?php echo get_template_directory_uri(); ?>/contact_Footer.mp4" type="video/mp4"></video>

jQuery Function

$(window).load(function(){    footer_lazyloader();});function footer_lazyloader() {    var $ = jQuery;    $("video.connect-bg source").each(function(){        var sourceFile = $(this).attr('data-src');        $(this).attr('src',sourceFile);    });}