My doomed 408 build

I’m sorry about your misfortune, and I believe the root cause of the failure is of no fault of yours.

Either a substandard set of lifters was used, or....... the not-up-to-the-task-of hyd roller-duty valve springs allowed for a loss of valvetrain control, which set up a situation where the cam lobe was able to smack the lifter wheel.
They won’t take very much of that before something breaks.

I don’t know what the lifter link bar situation you have is, but I’d also look closely for witness marks where the link bars were contacting the block, which if happening doesn’t end well.