Well it seems to me that you're the one who's not following cycling, at least not for long, or you simply don't understand it.
If the leader is weaker than top domestique, well than you have the wrong leader, which will be a case with Aru who is weaker than Landa especially on the climbs and could easily finish behind him in the GC. Leadership isn't eternal, you could change it during the race, you know.
Contador went after Landa exactly because it was him, he decided to marked them both, because they're both threats in the GC, as you can see, one is 2nd the other is 4th
Contador did attacked, in case you didn't noticed, it was counter move to Landa's first attack, when he saw that Aru is dropped, and he eased off only when he saw he can't drop Landa, he didn't want to risk a counter move
Landa attack accomplished little in terms of GC, i agree, he should of attacked way earlier, but probably his team didn't let him. But he accomplished much in terms of self confidence, he knows now that he can fight with Contador in mountains, and if Martinelli is smart he will play on both cards, him and Aru, cause this is the only way they can hope to beat Contador. If they ride strictly for Aru, it's a game over
Landa is not a one-hit wonder, that's exactly why I think you don't following cycling much, he was always a talented climber, back in his Euskaltel days, he just hasn't proven himself in GT's till now.
And so what if everyone sees it, you think Contador didn't knew that. What if for example Contador goes, Aru can't follow, but Landa can, what would you do if you are Martinelli, what would you say? My guess is that you would say to Landa to pace Aru and minimize the damage, because Aru is freaking leader! The road decides who the leader is. What about Richie Porte, he's the leader in Sky, why didn't Konig paced him today? By your logic he should