I'm surprised at Winston and Franklin - I'm pretty confident that the bump/spike was due to Churchill and Roosevelt. Barack unfortunately was not in the list, so we can't compare that. But compare that to Joseph (Stalin), also a common name, which didn't experience a dip. But then again, neither did Adolph.
Is there a name that experienced a dip, and then became popular again, due to a significant person?
Realistically, how frequently to you hear the infamous 20th century leader referred to as "Adolph Hitler" today, as opposed to just "Hitler" (or, "literally Hitler")? I think by 2029 the fact that his first name was "Adolph" will fall into the pile of "mostly obscure history facts".
Things can change in another generation. By 2029, American kids born after 9/11 will be having and naming kids of their own, so "Osama" might be the #1 name to avoid, with WW2 less significant in their perceptions.
Well it's bound to come back someday I guess, 2029 is as good a time as any :)