So without consulting some of my books off the shelf to give you absolute precision, since it's been a few since I've read anything, the overview of Sykes Picot is two ridiculous humans, Mark Sykes and Francios Picot, met secretly and came up with a way to divide the Middle East into four areas to be essentially exploited for the gain of the main allied powers. This was basically pre planning for the fall of the Ottomans and how to maximize profit. Which in and of itself is very trifling, but it's taken to 11 by the fact that both of these guys were of the era of the gentleman amateur, which if you aren't familiar was a huge thing among the landed and aristocratic in the 19th century going into the 20th, and mainly means they are morons who had no fucking idea what they were doing. Sykes is more the amateur archetype, and Picot more of a sniveling shithead, but that isn't a meaningful distinction of what were are talking about here.
Long term it gave us Syria, Iraq, Jordan that was grouped by no rational state of affairs on the ground, be it demographics, history, tribal, or anything. Syria was supposed to be an Arab homeland, which didn't happen and pissed everyone off, Iraq was essentially for oil rights, and Jordan was the only one that actually survived in any reasonable form. The Syria debacle set the stage for Arab enmity for the west for generations just on its own. TA Lawrence called it at the time but was brushed off.
Then Balfour tacked on a Zionist homeland a year or two later into an already ridiculous situation, and the Arabs watched even more of their land be straight robbed.
You can blame basically all downstream carnage in the Mid East over this insanely idiotic farce. The rise of jihadism is a directly result of the economic hardships and mismatched leadership of this. You had rulers with no legitimacy in the eyes of the populous and no hope of any betterment of life. Then you have generational cycles of escalatory violence.