Nothing, AP item is garbage since the nerf of Rabadon, which is why you see AD mids over AP mids.
Brutalizer give early snowball potential plus building into late game items, haunting is good but does nothing past mid game, Lindary is pure garbage for most traditional APs and should never be build unless you want to do sustain damage or something like Amumu.
Also revolver is garbage after the nerfs. You get sustain but zero damage. WotA is just bad, unless you run double AP or something which means your already losing. Whereas Vamp specter now do the same as revolver, except is MUCH cheaper plus actually build into something that isn't garbage.
The only "good" AP items now are murmana and DFG, but those are good for a small selection of APs. Hence that's all you see if it was a try hard match.
Reality is defined by your imagination, the catch is to convince yourself what is and what is not.