I was checking the "Links to Your Site" tool in the google search console and was very surprised by the result. I have hundreds of thousands of links from thousand sites(e.g. meetup.com, stockfresh.com being the top). All the links are to one page:
I have two questions - why did that happen? What can I do to stop it, is the disavow tool my only option?
It sounds like link bombing. There a couple of solutions to consider:
If you see negative impact in your search ranking then you can send feedback report to Google team directly from Google Search Console. The team can later remove the links if your request/report will be approved (after a couple of days/weeks).
You can just ignore these links - Google might also detect them as artificial/low value and ignore it.
If you think that these links can harm your website ranking then you can submit disavow file. In this case remember to be very careful in order not to disavow your positive/natural backlinks at the same time.