how can i make them not stupid ? i mean if i make a race with 20 cars , half of them crash and all of them want to go at the same line without overtaking.

is there a way to make them drive in diffrent lines and behaive smarter more random and smarter ?

thx for help :]

As far as I know, AI is just retarded. You'll just get a free bump for now, maybe someone else can help.

As you said, the AI is retarded. They had the ability to learn, but I think I once read that they no longer can. So, if you want to play normally, go online.

Even when they could learn, and before tire temp/wear was added, introducing variability to lines from lap to lap, the AI were never very fast. They always drove extremely conservatively.

And when you think about the fact that AI on Pro used to leave me seconds behind on Blackwood a few years ago.

Yep, the AIs don't learn anymore afaik. Was taken out some patches ago.
The only thing I can suggest to make the AIs less stupid is to experiment with setups, a correct setup may stop all the crashing out but certainly won't stop them using you as brakes :P