Why did my mower throw a rod?

I WAS mowing on a 45 degree incline( I was tilting to the left and right, not forward/backwards). It ran slower and slower until it blew with a loud "clank". It was a free rider mower and my first time mowing a friends yard for him. I am rebuilding it...think it was the incline that killed her, or should I be looking into other causes? thanks!