Well, that’s obvious. But the 778G wasn’t released much later than the 750G. As a systems integrator, like Fairphone is, they probably get an NDA preview of what’s to come to base their roadmap on. Just speculating based on my own experience in the tech industry. They probably knew that the 778G was coming and would only cause a few months of delay to go for that one, in order to support a more future-proof phone. Really sucks that it’s the 750G, aka, 750meh 
And by the way, the screenprotector and case are only available by the end of November. So it seems like Fairphone could use that extra time 