The Cretaceous-Paleocene event is dated to 66m years ago [1]. The crater has been dated to 65m years ago [2]. The deccan traps was from 63-69m years ago with the bulk of activity 66m years ago [3].
Obviously both the volcano and the meteor were life-changing events. Of the three events the fossil record analysis is the hardest to analyse. But there are indications that the volcanos main activity may have preceded the meteor and that while the meteor did obviously contribute may not have been the main cause of the extinction. IE the dinosaurs may have been on their way out before it, or it may have been a "combination" of the two.
[1] https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_e...
The global mass extinction killed things that can be much more precisely dated than dinosaurs. Forams, for example, go extinct right at the impact boundary, cut off like a knife.
The main point of the article is that the issue is far from settled, and that evidence for both sides is lacking. Until the consensus is reached through scientific means (instead of bullying) the matter is not closed.
How these two phenomena can be equally the cause of the mass extinction at the end of Cretaceous?
Two reasons, at least. The first is the uncertainty about how rapid was the decline of Life. Any geologic date has an error, so it is extremely hard to assess the velocity of geological events. Around the K/T boundary most rock samples cannot be dated with a precision greater than a million year, that means that 2 separate events have the same probability to be coeval or separated by hundreds of thousands years with 95% confidence. In these case the uncertainty cannot allow us to distinguish an abrupt event from a slow one. More precisely, some rocks can actually be dated with an error of ~10000 years, like the iridium anomaly, or like the Deccan's lava but forams does not live inside lava. So you have to correlate events, to find proxy signals like changes in water geochemistry and so on. This increases uncertainties when dealing with fossils, and may be an easy way to denigrate palaeontological studies, but there are still evidences of a progressive decline.
The second reason is that the decline in marine ecosystems was sharp after the iridium anomaly, but we cannot explain why that precise impact killed big reptiles on sea and land whereas hundreds of other asteroids that hit the Earth during mesozoic had not. It was surely not the asteroid impact alone. There are evidences that all the mass extinction events are not instantaneous, but they are all related to a sequence of (misfortunated) events in rapid sequence. The emplacement of igneous provinces has proven to be a common menace for life on Earth. Asteroids too.
What we actually "read" in the rocks is that Deccan's traps paved the way, the Yucatan impact provided a massive stroke, and the closeness of these two events finished the survivors. In my opinion the "war" between scientists was more an US phenomenon related to their need to get access to NSF funds. The cool one got all.
But, unfortunately, just because we like something, doesn't mean it really went down that way. And rightfully so, a horde of nerds will come out of the woodwork, to inform us if we were to claim the validity of an event, without true evidence in hand.
Either way, it won't stop me from harboring a deep suspicion that this is exactly what happened.
Mostly, my own belief is founded in similar conceptual origins for the moon.
On Mercury, it seems the impact that created the Caloris basin [1] may also have created a seriously busted-up region at its antipode (opposite on the planet from the impact) [2]. This may have happened due to shock waves propagating through Mercury's interior, focused by reflection at the planet's surface onto an area opposite the impact. There are alternate theories.
A few years ago, I looked into whether the Deccan Traps eruptions might have been either triggered or enhanced by similar antipodal seismic wave energy from the Chicxulub impact. Based on Earth's continental positions about 65M years ago, it seemed possible, maybe plausible. There were some papers discussing the possibility, but I don't have the data at hand.
[1] https://en.wikipedia.org/wiki/Caloris_Planitia [2] https://en.wikipedia.org/wiki/Caloris_Planitia#Antipodal_cha...
Could it be worked backwards, there a re a number of flood basalts, some as recently as 10mya, is there any evidence of impacts for any others? Or is there some reason the Deccan traps stand out compared to the others?
It's very human to want to connect these events into a cohesive narrative, but there is still the possibility that they were independent events in our universe.