How long can you keep tuna in jar with olive oil
No, it is not safe anymore.

The scombridae family of fish (mackerels, tunas, bonitos) decay in a way that does not necessarily cause a bad smell, as the bacteria just convert amino acids of the fish into a harmful version. The bacteria that does this is unfortunately facultative anaerobic, which means it prefers oxygen, but will do without, too.

So, the safety of the tuna can relies on the initial heating and keeping bacteria out with the airtight can, not so much on the oil.