Why and how is ‘grandeur’ associated with the ‘mighty dead?’

‘Mighty dead’ are those who performed great noble deeds throughout their life, people now remember them for their bravery.
The ‘grandeur’ is associated with the ‘mighty dead’ for their noble works and the beautiful legacy they have.

Final Answer:
The ‘grandeur’ is given to the ‘mighty dead.’
Mighty dead are those who had an honorable and noble life, the grandeur is given to them in honor.