What went wrong with these cam bearings?

Here's a suggestion from an 80+ year old friend of mine that has rebuilt many engines. When the parts come back from machining, and after everythings cleaned and blown out, coat all the bearing surfaces with Vaseline prior to assembly because in his experince, the most critical time for a rebuilt engine is when it's first fired. Then, a change of oil and filter after the first few hundred miles. :)