I doubt all or most of the lifters failed just sitting there.

What oil is in the motor?

If you have "thicker" oil in it, and the spring pressure has bled the lifters down, then they may be having a hard time getting the air bled back out of them with thick cold oil in the motor.

Also, if you have the pro magnum rockers, and not a lot of preload on the lifters, I've seen where pushrods can fall out on start-up after the lifters have bled down.
The pushrod cup on the rocker isn't very deep, and if the lifter is bottomed out and doesn't recover quick enough on start-up...... The pushrods can fall out of position.

I have not seen or heard of this happening with rockers that use ball and cup pushrods.