Bulk revert of unintended Develop steps

I did something really dumb! I was adjusting a single photo, with 3 distinct steps, in the Develop module, but I accidentally auto-synched to 10,521 other photos (my 5 star collection). One by one, I can open the history pane and click "clear history above this step" but how do I do that for the other 10,520 photos in bulk?

If it is any help, I had exported each and every one of the photos before I took these steps. So, alternatively, is there are way of reverting the catalog to its condition at the time of the export?

Sadly, I did not back up the catalog prior to or subsequent to the export. Dumb dumb dumb.