I have a craftsman riding mower with 19.5 engine an 42 inch cut. When you engage blades or let off clutch it goes dead. When it is running you can disconnect the safety switches an it will run ! What is the problem ?

Most common is the seat switch.
It thinks there's no one on the seat,
Luck

I put a jumper on it an it still does it

I disconnected the switches when it was running and everything was OK

It could be a open circuit switch,
Jumping it would close it.
Some are closed some are open.
Luck