The first I heard of Cloudflare was a recommendation from someone who used to DDoS websites (and yes they've been arrested for related crimes, long story), and I thought "what the heck is Cloudflare" then over the coming years, I kept seeing other friends using it. It's really interesting that Cloudflare was able to pop into a market that Akamai could have snagged for themselves or outright tried to buy out Cloudflar…
My point is that it’s very very hard to know in advance that a startup is going to be awesome at marketing. Their tech was not, on its own, a giant moat or a “must have” standout. So I can see why some VCs shrugged.