why are some elderly people so mean

for context, i was stopped around i12 katong area by an elderly lady who wanted to head to haig rd market centre. i searched up directions and told her she could take certain buses that would drop her off nearby the hawker, but she refused and mentioned someone told her to walk straight and turn left. which is true, you could do that but its going to be a hell of a long journey since you’re walking, not to mention it was quite sunny.

she agreed and so i decided to accompany her because she clearly didn’t know the way, and what if something happened to her during the journey? it’s not like there’s bus stops or sheltered walkways down that stretch of road.

all along she was complaining about the heat and the walk and i was fine with it because i felt the same way. she was curious and kept asking me where we were, that’s fine too - i just reassured her continuously since she wasn’t familiar with the place. made small chat and asked about her life in an attempt to make the walk less tedious and to keep her mind off of negativity.

but halfway through she started to proclaim loudly and accuse me of playing her for a fool and trying to mislead her. i reassured her yet again and told her i myself wasn’t from the area neither did i come here often so i was following the gps to the best of my abilities. i even pointed out the mall at the end of the street and told her the market centre was right beside it, if she wanted to she could take the mrt next time.

then she asked me what were the block numbers of the buildings around us, i looked around to see signs depicting the numbers, after which she started to dramatically express in her mother tongue, “oh my god you don’t even know where we are” and i was taken aback by it.

but once we reached her destination it was like a switch was flipped because she began thanking and complimenting me, even wanting to treat me to lunch.

so my question is, genuinely, why do some elderly people have a tendency to turn negative easily and scold others without a second thought? i am not looking down on them nor will i refrain from assisting them again in the future, i just want to understand how their behaviours came to be.