You’ve definitely gotten a lot of life out of your water heater, but nothing lasts forever. It’s great you have a home insurance policy, and while it can occasionally provide coverage for broken water heaters, in this instance you won’t have coverage under your home insurance.
Since your water heater is close to 40 years old, it’s unlikely something other than age caused its demise.
That said, if fire, freezing, or a similar event caused the damage, it’s worth reaching out to your insurance company. If the damage was accidental and sudden, you could have coverage.