Why is henry so intent on obliterating memory of everything done by one party or the other in the years immediately prior to his coronation as king of france?

See explanation below.

Explanation:

Prince Henry of Navarre was a Protestant in a Roman Catholic country. His ascent to the throne happened in the midst of the French wars of religion.

He decided to convert to Catholicism to be accepted by the people but he also wanted to protect the protestant people against religiously motivated attacks and he wanted to establish peace among its people. That is why he issued the Edict of Nantes in which he establishes religious tolerance (before him there was one king and one faith).

He thought that by obliterating memory of everything done by the previous parties (wars of religion), his kingdom will achieve peace.

yes it does because it does