So, I found a random website that discusses how old batteries can randomly fail due to high heat regardless of how maintained they are:
https://www.odysseybattery.com/news/...e-summer-heat/
"If a battery has a design life of six years at 77°F (25°C), and the battery spent its life at 95°F (35°C), then its delivered service life would be three years. This dramatic reduction in delivered service life can cause older batteries to suddenly fail in high heat because the accelerated failure rate occurs without warning."
"Lead-calcium AGM batteries are similar to lead-calcium/acid flooded batteries as both have continuous grid corrosion (galvanic corrosion) and this issue is increased due to high heat."