Jump Starting Proved More Effective than Trickle Charging My Discharged (to 5v) Lead-Acid Car Battery

As the title suggests ya'll, I had a lead-acid car battery discharge to 5v which I first tried to trickle charge. I attempted charging at 5 and then 10 amps, but couldn't get the pack to raise above 5v.

I was super bummed because it was fairly new, having got it just 2 years prior and had kept it well charged. So I said fuck it, I'll try jumping it! I jumped it, drove it around for a bit but noticed the charge was still a bit low, since it was reading around 12 volts while the alternator was running. I ended up putting it back on the trickle charger and got it to later read 14.4v while the alternator is running.

So, I'm curious if ya'll would know how this could happen? It's surprising to me because I've always trickle charged when jumping doesn't do the trick (didn't have a second car to jump with at first this time).