My GP checked my BP readings that would have been taken over the years and they were never high. Cardiologist asked if direct family had a history and if not he said it’s blood pressure .
My GP said my blood pressure would have to be high for years to cause it. He also said blood pressure doesn’t cause it , if the potential for it is there , it aggravates it.
I don’t smoke , did a little a few years ago for about a year , maybe 3 or 4 a day during a stressful time at home . And when I was a young adult would smoke when I went out but never outside that and that was over 30 years ago . Again I would think I’d have to be a fairly regular 10 to 20 a day for years to cause it .
So maybe a predisposition there ?

Mine was caused by my bicuspid valve which is hereditary. Had surgery March 6th. They replaced the aneurysm with a graft, repaired the valve and also repaired the aortic root. I’m doing well.

I believe heavy lifting can be an issue. My husband's cardiologists have warned against this.
My husband has two cousins with ascending aortic aneurysms - and one also has a descending aneurysm and an abdominal aneurysm. Both cousins were very health conscious and went to gyms where they did weight lifting.
My husband did heavy lifting working on projects around the house. He doesn't do that anymore.!