I've googled it and found the post I think you were referring to. It does seem like they may have been closer in the past than I thought, but I wouldn't read too much into a Facebook post from one professional promoting another and an event involving the two of them.
As for today, I think undeniably it is primarily about marketing - creating a rivalry to generate attention. That said, I don't think that rivalry has totally been plucked out of nowhere & I stand by my view that interactions between the two always seem a little awkward. Compare them to say Shaw and Hall, who are unmistakably close friends which reflects in the way they interact. I don't believe they dislike each other but with those sorts of egos some tension is often unavoidable.
And I wouldn't underestimate the impact Thor's actions comments in 2017 could have. Hall had just achieved what he had dedicated the majority of his life towards. That is the moment that defines his life. Thor's comments have the effect of undermining that achievement, disputing its legitimacy. That's gonna piss him off. To me it seems like Thor and Hall are acquaintances who exchange pleasantries and some small talk when they meet but that's the extent of their relationship - Hall's own comments hardly sound like how someone would describe an actual friend, more like a colleague: 'We got on, we talked, we respected each other.'