It could be anything, but based on the subject matter it is perfectly reasonable to conclude that what you suggest is unlikely. Your case that he wrote about Lincoln in those books is wholly speculative and without a shred of evidence, thereby making it insufficient to hold up as a matter of fact or even factual assumption.
So, we have on the one hand, clear and irrefutable evidence that Dilorenzo is a Lincoln fetishist
No we don't. First off, I'm not quite sure what a "Lincoln fetishist" is, nor do you seem to beyond tossing out that term as an intended pejorative. Second, 17 editorials on Lincoln is not at all unreasonable or excessive from an author whose most widely published and recent book is a Lincoln biography. In fact you will probably find that most people who have written a widely circulated book on Lincoln have written AT LEAST 17 short articles on him as well, if not other books. And though that is also certaintly true of such notables as Harry Jaffa, Jim McPherson, and Eric Foner for some reason I doubt you would ever accuse either of them of having a "Lincoln fetish." Third, as has been demonstrated repeatedly, DiLorenzo has written at least 10 other books and who knows how many academic journal articles. All 10 of those other books are on things such as health care policy, the economics of charity and other things with no indication whatsoever beyond your own blind and wholly unsubstantiated speculation that they mention so much as a word about Lincoln. They constitute a greater volume of his work than his one book on Lincoln and those editorials on the same subject.
We know that when he finally got to write HIS OWN book--and there is only one of those--
Since when was there anything wrong with coauthoring a book with another expert in a given field? Surely you are not suggesting that Bennett chose the subject of those other 10 books and forced it upon Dilorenzo as an unwilling coauthor!
Even though 17 of his most recent 17 columns and his only book deal with Lincoln.
Funny. I see at least 10 other books in which his name appears on the cover and title page. But, of course, you are not interested in an honest portrayal of his work so you make up excuses by which you may continue to perpetrate your attacks upon him without having to address the consequences upon your claims that their existence creates.
That's my point. And since we both admit that fact, we can't really safely assume anything. I hope it's raining where you are.