>>212273933The energy relased by the impact that created the Chicxulub crater is more than sufficient to fuck up the entire planet's biosphere for centuries if not for many millenia. Just all the ash, soot and debri released into the upper atmosphere and low orbit from the impact and the forest fires etc it caused, would have been enough to lead to massive global cooling/global winter that lasted for who potentially hundreds of fucking years. There is a reason nothing living on land that weighted more than 10 kilograms survived the extinction event besides maybe some crocodilian species.
Out of the dinosaur extinction theories we have, the fuck huge rock from space is both the most plausible at the moment, and the one we have geological evidence for as well.