@JAC this is a good question and certainly one that will trigger debate. Nord has a good track record for privacy with a no log policy, and has an independent audit to certify this as fact.
They also have the most number of servers scattered around the globe and also pioneered NordLynx which is based on the their existing Wireguard protocol.
I suspect much of their popularity comes down to their marketing as you suggest with YouTube influencers and affiliate links, although they aren’t the only brand leveraging this area.