Every single thing you listed has a purpose.
> the background image
is a blurry gradient of colors magenta and orange, angled off-axis. In other words, the complete opposite of the page contents: Sharp black and white precisely-aligned text.
The purpose of a background is to contrast the foreground. Mission accomplished.
> the colour of the toolbar
is one of the only persistently consistent visual elements across the entire website, which features many very different color schemes in its content. Take this page [0] for instance; as the menu elements you refer to lie on a higher level of interface hierarchy, this color of the toolbar sets the topmost brand tone of the entire website.
[0] https://hypertele.fi/d9a64d59472ad05b
> the right alignment of the text
Quoting the very page under discussion:
When your eyes read to the end of a line of text, they have to jump to the beginning of the next one. Left-justified text causes all lines to start at the same vertical, making your eyes sometimes miss the jump and begin reading a wrong line. This is why you're sometimes reading the same line twice by accident. By right-justifying instead, the left edge of the text is made variying, and your eyes have an easier time picking the correct next line.
I've spent the last 16 months working on this app/site. It's my passion side project to build a functional desktop environment in the browser.
Here is the source code: https://github.com/DustinBrett/daedalOS