I'm not sure if I believe Alonso knew as well but I don't think Piquet has an axe to grind with Alonso?
Ecclestone: "Nelson told me that he is going to do everything he can to destroy Briatore."
Piquet is trying to do as much damage as possible to Briatore, and because that there are important reasons to go against Alonso:
* Alonso and Briatore are close friends, Alonso always says he's in F1 thanks to Flavio Briatore, more or less same relationship Lewis Hamilton and Ron Dennis had.
* Alonso declared to press (Brazilian included) that he considers impossible that Briatore ordered Piquet to crash on propose, which it's the same as say Piquet is making false accusations. Others would shut up and wait but... Alonso is Alonso, he can't shut up, he just says what he thinks at that precise moment...
* If Alonso is inside conspiracy, then what Piquet Jr. says about not receiving same material and being under a boycott would appear as possible and logical, so he can say he don't really sucks like it seemed.
But more than this, what Piquet Sr. says is just a guess:
"Fernando knew everything. He couldn't ignore it."
Anyway, in radio transcriptions you can read how Alonso is asking why they are changing his strategy from 3 to 2 stops, as well as his engineer, and it's Pat Symonds who convinces them to change, in theory to avoid traffic when rejoining.
No matter what happens, the one taking the biggest damage is Piquet Jr., his racing career (as driver and as anything else) is just over, if he crashed his car on propose he made the biggest mistake of his life.
Cya!.