You say you republished the content from the cached page. I think you mean that you copied the content and created a new post with that content, correct?
Did you delete the old post?
The problem you are facing is this: your comments and a lot of other stuff is connected to your original post by post ID-- a number in the database that you rarely ever see unless you know where to look. If you have created a new post it is going to have a new ID. To get things straight those IDs are going to have to be juggled around. Several general approaches come to mind:
- If you didn't delete the original post, you might be able to change its ID, then change the ID of the post you just created to match the original post's ID. Then delete the original, using some non-WordPress mechanism such as PhpMyAdmin.
- If you didn't delete the original post, another option would be to dig through the database and change the IDs for the comments to match the new post's ID. I can't think of anything to really recommend this over the first approach, and it seems much more prone to error.
- If you didn't delete the original post, you might be able to get that post back. If you can explain exactly what you did you might be able to undo it. This is probably the place to start.
- If you have deleted the original post though the WordPress backend, you really have no choice but to copy and paste the comments into new comments on the new post since deleting the old one would have removed the comments from the database as well.
The first two option really qualify as hacks and involve direct manipulation of database content. There is therefore some risk.
There are some "move comment" plugins, but given your situation I don't know if any of them will work (The first in that list has not been updated since 2008. I do not recommend trying that one.)
So let's go with item #3 and see what happens.
First, though, save that cached page to you hard disk. Caches expire. You don't want that.
Second, backup your WordPress database.