I could be wrong but my guess would be that the catastrophic decline of Bald Eagles in the lower 48 was more due to indiscriminate shootings than DDT. See predator and shoot it.
And it's subsequent return has to do with being on the protected list and a change in mindset where only the most determined to break the law and thumb their nose at the rules that govern wildlife would shoot them today.
They are thick as rats at Lake of the Woods. Have been for decades. Had one in a tree in my backyard when I lived in Winnipeg....old part of the city, very close to downtown. Only thing that ever scared my cat. Now THAT was panic personified!
