From an evolutionary/physiology standpoint, human bipedal locomotion freed up our forelimbs/arms such that "limb assisted pointing" became possible/practical. Perhaps why elephants seem to grasp human pointing is because their trunks serve as a similarly "free" limb that they can use to point at things. Sort of like convergent evolution, but behavioral rather than morphological...

> "When they detect something alarming, they characteristically face towards it and raise their trunk above their head with the tip of the trunk pointed to [the danger]," Byrne said. "We've always thought they were sniffing the breeze, but maybe they're also pointing; our results suggest that's more than possible."

https://www.nationalgeographic.com/animals/article/131010-el...

I'd agree with GP here - pointing with a finger is a very specific variant, that's arguably cultural in nature. More fundamentally, pointing is about communicating to the other being they should focus their attention elsewhere, and where that elsewhere is. "Looking"/"facing" and associated body language is a more common form of doing this, and humans too do it and recognize it, even if no fingers are being moved.