Slot had a massive slice of luck in the summer after he joined, in that he failed to land any major signings for the season to come, so did nothing to disturb the basic balance of the side (and we can now see what that might have looked like). That combined with the lack of consistency among the traditional challengers and squeezing the last drops out of Salah, Van Dyke and Alexander-Arnold, was enough to see them home. To me, he looked very nervous early on last season, but seemed to Liverpoolise (i.e., become narcissistic) as results went in their favour, carried by the wave. I'm not sure he is really arrogant, but he is very Dutch and has that directness that sounds arrogant (to British ears, at least). In any event, it is most pleasing to see them squirm, even if only temporarily.
