Alonso only wasted his engine in the final laps, that's the only thing he accomplished. But I can understand why he did that --
he wanted to be as close to Schumacher as possible in the hope that he can induce Schumi to panic and make a driving error.
But he was simply too far to make any difference. And in fact, evenif Alonso caught up with Schumi, I am sure Michael can block him
for 3 more laps and still win the GP (remember, they are driving on the dry racing line to avoid a spin, so Alonso doesn't have much room to overtake anyway).
So tactically speaking, ALonso's "driving-like-hell" effort was foolish.