Further to the 'Battle of Conoco oilfield', from 8 February: slowly, very slowly, pieces of the puzzle are coming together.

Inside the U.S. coalition attack on Syrian forces in Deir-ez-Zor
...Pro-government outlets have made various claims about their losses: that zero deaths occurred,5. that all deaths were among local tribesmen,6. or that only 25 National Defense Force (NDF) fighters died.7. However, loyalist martyrdom reports paint a very different picture.

Within 24 hours, 22 martyrs “of the American aggression in Deir Ez Zor” had been named and at least 30 bodies had been brought back to the hospital in Suqaylabiyah.8. Of these men, only two were Deir-ez-Zor locals of the Bagarra tribe: Laith and Ashraf al-Bashir, sons of the influential Sheikh Nawaf al-Bashir.9. Of the remaining 20 fighters, seven were from the coastal governorate of Tartous, five from the coastal governorate of Latakia, and eight from Hama.10. Two of the men from Tartous were high ranking officers: Brigadier General Yusuf Haider and Lieutenant Colonel Yasser Essa. Lieutenant Colonel Essa and eight other fighters were identified as members of the enigmatic “ISIS Hunters,” a small Russian-equipped, well-trained, and well-armed militia historically operating in Syria’s east.11. Brigadier General Haider was identified by a relative as a Russian linguist.12.
...

Furthermore, in June 2017 the St. Petersburg-based Fontanka organisation broke the news that the new gas and oil company Euro Polis and the state-owned General Petroleum Corporation had signed contracts granting them the rights to 25% of any oil and gas production at facilities captured by “its contractors” from ISIS.18. This was confirmed by the Associated Press in December 2017.19. The Fontanka report further identified “ISIS Hunters” as holding “contractual obligations” to Euro Polis for securing those oil and gas fields. Fontanka also published a video filmed by Russian fighters near Palmyra, Homs, identical to an earlier video published by the official ISIS Hunters Twitter page.20.
...

Shortly after the skirmish, a mid-level Syrian fighter posted his account of what happened on Facebook: “At around 10:45pm last night, the Syrian Arab Army and its friends began the battle for the liberation of the Conoco gas fields controlled by the Kurdish militias.”21. Two sources close to another Russian private military contractor operating in Syria, Wagner PMC, further claimed there were Russian casualties in the battle.22.23. The high concentration of ISIS Hunters among the attacking forces, the presence of a Russian linguist, and the intention of seizing the largest gas fields in Deir-ez-Zor implies that this attack was instigated either by Wagner PMC or by Russian leaders within the ISIS Hunters, potentially at the behest of General Petroleum Corporation.
...
Now, this is making things as complicated as it's explaining them.

Crucial is the notion that - according to this article - the push for Conoco oilfield was financially motivated. It's simply so that the contractor gets 25% of the oil revenue from captured facilities. This prompted multiple groups into getting involved in the race.

Mind: oilfields are private ownership of strategic importance. Nothing that belongs to whoever stumbles into one. Wars, uprisings, insurgencies, proxy wars, legitimate or illegitimate governments, mass murderers or whatever is in power - or not: there are contracts for oilfields, assigning the ownership to specific parties. In this case it's the Conoco. And Conoco gives 25% of the profit to anybody 'liberating' its facility there.

Along that line, no surprise that multiple parties got involved ... or that the US-supported PKK/PYD/YPG/SDF-conglomerate 'defended with all means on hand': i.e. the PKK rose the US flag like its underwear and the CENTCOM was promptly on the scene.

That's pure war profiteering - by all the involved parties. At least two of these paid a hefty price for losing that race.