This situation is best summed up by Kevin's post here;
I looked at Google Search Console today and I seem to have almost 20,000 more pages crawled on my site that I didn’t create and are not in my CMS. All of these new pages have these long Chinese slugs and lead to a 404. Wondering if anyone else has experienced this. My site is completely hosted on Webflow.
And also by Josh's response & references;
this just means that a random site somewhere has created these random links to your site on one of their own pages, which Google has then crawled. But it doesn’t necessarily harm your site
Google developer docs;
Q: Most of my 404 errors are for bizarro URLs that never existed on my site. What's up with that? Where did they come from?
A: If Google finds a link somewhere on the web that points to a URL on your domain, it may try to crawl that link, whether any content actually exists there or not; and when it does, your server should return a 404 if there's nothing there to find. These links could be caused by someone making a typo when linking to you, some type of misconfiguration (if the links are automatically generated, for example, by a CMS), or by Google's increased efforts to recognize and crawl links embedded in JavaScript or other embedded content; or they may be part of a quick check from our side to see how your server handles unknown URLs, to name just a few. If you see 404 errors reported in Webmaster Tools for URLs that don't exist on your site, you can safely ignore them. We don't know which URLs are important to you vs. which are supposed to 404, so we show you all the 404 errors we found on your site and let you decide which, if any, require your attention.
