what can cause a cam chain to be cut

I activated a launch control on a BMW m50b25 non vanos engine as shown in the picture. while testing it, the cam chain was cut and cylinder one bent a valve, not sure if it is the intake or exhaust yet. i want to know the reason behind what happened because I'm confused

I commented elsewhere, but to expand on that, that amount of side flexability would suggest chain stretch before failure.

If you would post a picture of the broken ends, it might help.

This is the engine with the faulty tensioner and broken sprocket teeth, isn't it?

You'll probably find there's much more damage than you think - there may be multiple damaged valves, seats, the head may even be destroyed, as may the block from piston damage - hopefully not, and it's just some bent valve heads and marked pistons.

this is all pics i have, yeah this is the motor you are talking about. I don't get you can you explain in more details please. sorry

You've likely resolved this, but spark cut limiting is rather rough on things, and while chain systems are more durable, damage is still possible if the tuning of the spark cut and timing reduction is aggressive.