Just want to link this thread with my issue.
When either the Defaults/Bookmarks or Defaults/Preferences files get corrupted, Brave will crash on launch. I’ve been through this three times now where I had to rebuild/restore my bookmarks. The only thing that works at this point is to regularly make a backup of your bookmarks by exporting them from the bookmarks manager page, then it’s fairly simple to just re-import the bookmarks if you otherwise have to trash the Bookmarks preference file and/or all of your preferences. But if you don’t have a backup of the bookmarks, it’s can be difficult to fix the bookmarks file. You have to know how to read JSON and perhaps use a language like Python as I did to evaluate and debug the JSON to find the problems in the file.
The bottom line is, when Brave crashes or quits due to a locked up web page, or for any other reason, it routinely corrupts its own Preferences and Bookmarks to the point where the app won’t launch anymore. They really need to fix this issue. In the meantime, backup your bookmarks regularly (or keep snapshot backups of your system so you can just restore the entire preferences folder from a time prior to the latest crash).