I can't speak to the Treaty of Trianon but it's worth emphasizing, as you touch on, that Sykes-Picot was about spheres of influence, not borders. I've written about this pretty extensively (for example, here) because while Sykes-Picot is used as a short hand for "European Border Meddling" it doesn't actually resemble the current borders of the Middle East on any substantive point.

I would also argue against the idea that the European powers were "splitting of ethnic populations by the Western powers with little care for where the borders landed." Few reasons for that 1. because they often merged multiple groups intentionally, with local backing (as in Iraq), fully aware of the challenges of doing so but believing it would result in long-term stability 2. When they tried to divide states along ethnic lines (as with the French division of Syria) this was rejected by the local populace, and 3. it implies that there is some "natural" ethno-national drawing of the borders of the Middle East that would have prevented conflict, which I simply do not believe to be the case, particularly given the limitations to European power (e.g. Turkey's retaining, by force of arms, most of the predominantly Kuridish areas in the treaty of Lausanne), the introduction of Zionism as a source of conflict, and as above, the desire of local rulers to control territories of maximum extent and resistance of local peoples to being "divided and conquered" along narrower ethno-sectarian lines. If anything the trend of the early 20th century culminating in Nasserist Arab nationalism was for the whole-sale unification of these territories.

Sykes-Picot itself I think also must be understood in its wartime context as a negotiation between allied belligerent states and done in conjunction with other allies and would-be allies (i.e. Russia and Greece). Insofar as it disregarded ethno-sectarian divisions, so too did the Hussein-McMahon correspondences, the promise to the Arabs that Sykes-Picot infamously (and supposedly) broke. That, too, was a wartime promise and like Sykes-Picot ended up being re-negotiated in the peace. The British willingness to massively over-promise and under deliver, which was regarded with horror by the post-war negotiators who tried to untangle the mess, I think has to be thought of in its wartime context as being proposed and supported in large part by men whose first thought was to the butchery on the Western Front and trying to find some way to bring about a speedier conclusion to the war and to bolster British allies in their support for the war effort.

edit: phrasing