Simple. First, it uses a CDN (Cloudflare). Second, the site doesn't have 20 useless tracking scripts (I only see Google Analytics) or 10 useless pictures, the entire web page is only 446.37 KiB. The website is more than qualified to join the "1 MB Club" (recently discussed on HN, https://news.ycombinator.com/item?id=25151773). Third, all images are lazy-loaded (I see the WordPress plugin a3-lazy-load was used), so heavy images won't be downloaded until you need them. Fourth, it uses an aggressive caching policy:
> Cache-Control: max-age=31536000, public
> Expires: Sat, 04 Dec 2021 17:06:47 GMT
So after the first click, 95% of the static resources will be cached and it significantly reduce the download size, which is a good practice (add version number to the file name, so you can always use aggressive caching). Although it's sad to see the website digital.com has become a web hosting marketing site, but at least the site owner did do her SEO homework by not creating yet another toxic webpage, I can consider it a positive (or at least, non-negative) contribution to the web.