Do you know how old it is? Sometimes as batteries age the posts can get corrosion under them and push up like that, once it left the plastic that was a majority of the support. I believe the posts are mounted into the top and then bonded to the terminal in the battery when assembled. That situation is not unique to optima. Standard batteries usually tear the plastic up around the post when this happens, The optima case is so strong it managed to get the post out of the plastic. I have tried to open an optima before, it is not easy, we finally got a lid off of one by popping it off with a forklift. We were able to deform the case by throwing it in the air and letting it hit the concrete but it to the forklift to see the inside.

There should be a barcode on the battery. IIRC on the barcode the first 4 digits are the date. Like 8365 would be the last day of 2008, its been awhile but I believe that is how they are read. It might also have a standard battery code on top but I couldn't fine it by zooming in. It would be a 4 digit code and you would need the first two. A=January etc. So A8 would be January 2008, L8 would be december 2008 etc.

Oh, and get a proper AGM rated charger or maintainer.