"Given that lightning bolts tend to hit tall objects, especially in open areas, the height of giraffes may make them particularly vulnerable to fatal electrocution," Rockwood Conservation scientist Ciska Scheijen wrote in the African Journal of Ecology
This is a fantastic question.
Dang! I've never thought about it before. Burning to find the answer, I found:
https://www.iflscience.com/giraffes-really-are-more-vulnerable-to-lightning-strikes-because-of-their-ridiculous-necks-67427
There a link to the journal, but it's pay walled.
Un-paywalled link to journal.