Charles Guiteau had a long career prior to assassinating Garfield, as did Booth before assassinating Lincoln. While both committed assassinations, there was no point in time where you could have hired either to assassinate someone for you, it wasn't either of their professions.
One sentence fragment conveys that Lincoln was assassinated, the assassin's nationality, and the assassin's profession in 67 characters. The other conveys that Lincoln was assassinated and the assassin's nationality in 58 characters.
You like the wrong sentence. It's stylistically kooky, too: you need to point out that an assassin killed someone? That doesn't feel a little redundant to you?
> the man's profession is completely irrelevant
Hardly. But mostly it's strange that you'd want wikipedia to make that determination for you. It's not necessary.
> "Standard wikipedia formatting" being burying the lead is not a compelling defense.
Burying the lede would involve putting the information you're burying somewhere other than the middle of the first sentence of the first paragraph.
I find "an American stage actor who assassinated President Abraham Lincoln" to be a ridiculous introduction; it should read "an American assassin who killed President Abraham Lincoln" -- the man's profession is completely irrelevant; he is notable for this one act.
It isn't even consistently applied: Ted Kaczynski is listed as a domestic terrorist, Sirhan Sirhan is "a Palestinian Christian militant," but then Charles Guiteau is a "writer and lawyer."