Why? He took a non-existent line which could have no other outcome but to hit Sainz. Alonso was probably hoping Sainz would see him and take avoiding action. But at that point Alonso was so far behind Sainz had no chance even if he looked. And there was no reason to look, there should never be a car there.

And remember they check the data as well, at the speed Alonso was going he had no hope of making that corner in any decent way. If he hadn't crashed into Sainz he would have gone wide and lost a heap of time. The line didn't make sense and he took it anyway.

In of itself penalty points don't do anything. But Alonso should consider himself warned. If he continues this kind of driving, he will get more penalties. Russell was lucky not to be injured by that brake check. So Alonso is under a magnifying glass since then.

No I think it was fine. It such a clumsy move by Alonso made out of desperation. He hit sainz even though sainz was driving a line which was taking him off track. There was no universe where Alonso could have made that move while giving sainz enough space