Google has recently made a drastic change to the search results page, the left side toolbar has now been moved to the top. There are several reasons for this, a consistent look across devices, a cleaner page and so on.
But plenty of people don't like change and plenty of people had gotten used to the old search options and filters toolbar.
Since this is just a visual revamp and since it's just the placement of the toolbar that changed, the site looks exactly the same in every other aspect, you can imagine it's fairly easy to come up with something to get the old sidebar back.
And you'd be right, the good old Google is only one
userstyle (the updated link) away. Given that Google Search customizations are some of the most popular types of styles on userstyles.org, it's no surprise that something like this showed up there. In fact, it's very likely that there are similar styles out there.