Likely the battery was already low. Modern batteries are wonderful things, they have double the power they did 30 years ago, and are maintenance free. No checking the water, etc.
That, unfortunately, has nothing to do with the terminals on top, which seem to need a cleaning every 6 months. Those terminals stick up thru the case, as water tight as the designers can make them, they will push sulphuric fumes thru that area and it bathes the connection in a corrosive atmosphere. Those little felt rings that the auto parts stores push are actually helpful in keeping the fumes off the connection.
If the connections present too much voltage drop, the battery won't charge. I've seen some clean looking terminals that had enough hidden corrosion in the connection that a diagnostic load tester couldn't detect any current. Like it or not they need maintenance. And that goes for Optima's, too.
Charging a battery takes time. If a 500 CCA battery is down at 50% of it's power rating, then, charging at 10 amps with a bench charger hooked up, it's going to need 250 amps put back in. 250 / 10 equal 25 hours. Two hours won't even begin to do the job. And idling the car that long won't either. While the alternator puts out over 100 amps, the fuel injection, pump, circuits, etc consume up to 80% of its output, so, you're back to that 10 amp hour charge rate. Nobody is going to drive the car for 25 hours to charge it up. Jump starting it does nothing.
Batteries are rated in cranking amps output, but another rating on the label is reserve capacity. That's how long the battery will put out 25 amps of power at 80 degrees before falling below 10.5 VDC. Most will run at least 60 minutes. If you are running a big stereo system with sub woofer rated at 1000 watts, it will pull 25-30 amps all by itself - hence the fuse on the unit. If the battery was already discharged from corroded terminals, it's no wonder the battery was toast in 20 minutes.
Case in point, a few years ago someone pulled into the store off the Interstate with a complaint the headlights were flickering and the car starting to run badly. They had been on the road for four hours, running a 2500 watt stereo system off the normal alternator and single starting battery. Testing the battery showed about 15% power left - the system could not keep up with the draw from the stereo and had drained the battery nearly dead. The clue was the huge cable attached to the positive terminal. In every case that I have seen, the home installer had no clue that the system would easily exceed the power output of the alternator and drain the battery. The few shops locally will install another battery in the trunk for stereo power, but the downside is they seem to last about two years. That's pricey when it's a $150 Optima, but cheap up front compared to adding another alternator and drive system for $500+. Which is exactly what is required on ambulance chassis.
It's all about the math and nobody teaches it or writes it up in the owner's manual. Mostly School of Hard Knocks learning about it.