Dry, bad luck mate

Automotive batteries weren't designed to be flattened, your car being as original as it is, i expect its got a fairly aged battery on there, quite often flattening an older battery is enough to kill it

If you have to buy a new one spend a good few quid on a good branded one, ive had nothing but bad experiences with cheap unbranded batteries and refuse to buy them now, calcium batteries seem to last very well

And did you fix the alternator or buy a new one?