I have come across a couple of new books on the subject by Thomas Lorenzo that indicate it was the Tariffs aimed at the southern states that might have been a big reason..."
Thomas J. diLorenzo, while sometimes conservative, is a lying sack of Lost Cause apologetics, so if you are looking for modern excuses and justifications for Confederate actions, then diLorenzo is your guy, read him and weep.
diLorenzo's "The Real Lincoln: A New Look at Abraham Lincoln, His Agenda, and an Unnecessary War" is from 2003
diLorenzo's "Lincoln Unmasked: What You're Not Supposed to Know About Dishonest Abe" is from 2007.
But if you are looking for actual historical facts & reasons, you won't find those in Lorenzo's books.
In the cases of Secession beginning in December 1860 and Civil War beginning in April 1861, the reasons are not the same for each, and are perfectly obvious to anybody who studies source documents.
In the case of Secession, there were half a dozen major documents produced at the time, explaining their reasons why, and they gave several reasons of which slavery was, by far, the most important, and tariffs were seldom mentioned:
"Reasons for Secession" Documents before Fort Sumter -- % of words devoted to each reason
| Reasons for Secession | S. Carolina | Mississippi | Georgia | Texas | Rbt. Rhett | A. Stephens | AVERAGE OF 6 |
|---|---|---|---|---|---|---|---|
| Historical context | 41% | 20% | 23% | 21% | 20% | 20% | 24% |
| Slavery | 20% | 73% | 56% | 54% | 35% | 50% | 48% |
| States' Rights | 37% | 3% | 4% | 15% | 15% | 10% | 14% |
| Lincoln's election | 2% | 4% | 4% | 4% | 5% | 0% | 3% |
| Economic issues** | 0 | 0 | 15% | 0% | 25% | 20% | 10% |
| Military protection | 0 | 0 | 0 | 6% | 0% | 0% | 1% |
* Alabama listed only slavery in its "whereas" reasons for secession.
** Economic issues include tariffs, "fishing smacks" and other alleged favoritism to Northerners in Federal spending.
In the matter of who started war at Fort Sumter on April 12, 1861 -- if you are a devoted Lost Cause of the Confederacy acolyte, then obviously it was that evil devil, "Ape" Lincoln, on sending a "war fleet" to "invade" South Carolina's "sovereignty".
For everyone else, it's perfectly clear that Jefferson Davis intended to start Civil War at Forts Sumter and Pickens, regardless of what Lincoln did, or didn't, do.
***
I should mention here that diLorenzo was a favorite target of our FRiend, rockrr, and I wish I could still defer to rockrr's expertise on the subject.