The upset wasn't that surprising, this kind of thing happening is just a normal thing and sometimes some teams are just choking or getting psyched up that they're a win away from winning that when they lose one game, it eventually snowballs into a comeback for the other team.
By me it was highly anticipated matchup of this season . In my view after first two wins FPX assumed that victory was theirs they lost their temper and loosened their grip. Having such opponent as Team Top Esports challenging the victory in the final they they should have had better game management to unfold all their potential and dominate up to the end of game 5.