Ask HN: Why are some webpages sending double content?

I've noticed recently that some sites (for example: https://www.aerofs.com/blog/) seem to duplicate the content on the page.

The formatting makes the rendered page only show it once, but with some elements (cookies, Javascript) disabled, or just by viewing the source, it can be seen that the content appears twice.

Is this the results of a certain content managament system, or a particular framework ?

I can't imagine that sending double the content is particularly beneficial.