First of we need to understand one thing, there are many theories to what happened to the dinosaurs, most of this theories are based on science  and this theories are the collection of knowledge of many years by scientists. And of course there are other accounts that based only in canonical books that can’t be corroborated.
There are two major theories with large support and one being the intrinsic gradualist and extrinsic catastrophists.
First let put some common ground between this two theories about what happened to the dinosaurs.
- Climate change Scientist studying minerals and fossils from the Arctic Svalbard in Norway have found evidence for green house climate change causing a drop in global temperatures from 13 to 4 degrees at ocean level.
- There evidence that by the end of Cretaceous period the climate may had change so much creating a massive terrestrial disturbance which polluted the air creating acid rain, emission of poisonous gases and cooling creating something similar to a nuclear winter.
- There are evidence in many places around the globe of a thin layer of clay with an unusual high iridium, this could prove the there was a dust cloud around the planet.
- for more read this paper on this topic.
This theory implies the ultimate cause for the extinction was gradual; meaning that was a natural and gradual process taking several million years to occur.
One of the facts know from Cretaceous period is that there was increased volcanic activity. During a several million years of never stopping volcanic activity could have created enough dust and soot to block out direct sun light producing climate change.
During the late Cretaceous huge volcanics eruptions were spewing floods of lava which can been seen today. The chemical composition of the lava of rocks in India show that they originated in the Earth’s mantle since there is a rich concentration of iridium, this could explain the iridium layer.
Furthermore volcanic activity can not occur without the action of plate tectonics, during this period major changes in the organization of the continental plates were occurring.
The other theory that hold a lot support and evidence to explain what happened to the dinosaurs is extrinsic, meaning of a extraterrestrial nature and catastrophic. The main hypothesis was proposed in 1980 by Luis And Walter Alvarez of the University of California at Berkeley.
The hypothesis proposes that a large extraterrestrial object collided with Earth, this explosion could created enough dust to cause the climate change. The iridium layer is what prompted the team to blame an asteroid impact could explain what happened to dinosaurs.
Extraterrestrial material such a comets are bodies higher in iridium content than Earth’s crust, this help the team to figure out that the iridium layer has to be composed of dust from vaporized meteor.
Researchers found a likely candidate for the crater located at Chicxulub on the Yucatan Peninsula, Mexico. This crater was found in 1970s by geophysicists who had been looking for petroleum in the area. The age of the rocks around the impacted area shows to be around 66 millions years old, the end of the Cretaceous period which coincides with the other rest of the data and samples.
This extraterrestrial event could had triggered a cloud of super heated dust and ash that could had created a hash environment for life by covering the planet for years even decades with clouds and ashes.
The main problem with this theories is not easy to test and that most of the ages of the rocks that different evidence comes from are questionable since one evidence contradict the other theory and vice versa, this makes not possible to date to know for sure what happened to dinosaurs. Either of the theories are highly possible with strong evidence to back them up; There could also have been different or separate extinction events in the oceans and on land. If comet impacted Earth during a gradual decline, that may help explain the contradictory evidence.
Last we have the last theist idea and least likely to be real on how to explain what happened to the dinosaurs.
What Really Happened to the Dinosaurs? According to Ken Ham
Even tho there is 0 mention to animals that didn’t exist in the middle east where the bible was written by a nomad tribe. People tend to disturb reality to fit their agenda or just their believes. This article show this clearly. He adds:
According to the Bible: Dinosaurs first existed around 6,000 years ago.3 God made the dinosaurs, along with the other land animals, on Day 6 of the Creation Week (Genesis 1:20–25, (31)). Adam and Eve were also made on Day 6—so dinosaurs lived at the same time as people, not separated by eons of time.
First there is not mention of such a thing in the bible, that is intellectually dishonest to say since is basic knowledge the dinosaurs did not share the planet with mammals as we know them today; This show is just a sad and pathetic try to cover up non sense from an old book and make sense out of evidence to delude people to believe no sense by covering or changing the reality.