I noticed a video titled something like "What is an NFT?" and immediately thought the title is wrong and it should be "what is a NFT?" But after trying to pronounce it with "a" I understand (I think) why people say and write "an NFT". Also did some searching and found both "an NFT" and "a NFT" are used for videos and articles.
Is the easy pronunciation what makes people use "an NFT" or there is some rule for why "an" is used?