But of course an asteroid strike may create very favorable conditions for fossilization.
The hypothesis is that it was formed from the rapid drainage of a flooded plain, and that the flood was probably caused by the Chicxulub event.
If you're going to answer "parsimony", what if these events aren't independent?
(I'm not a paleontologist)
Shoemaker-Levy orbited Jupiter for quite a while before it broke up and went in.
The collision of comet Shoemaker-Levy with Jupiter occurred as several distinct impacts, due to gravitational disruption of the comet in a previous close encounter with the planet. Something similar is clearly possible on Earth (perhaps even gravitational dispersion of a comet passing close to the Moon just before impact?) but the Chicxulub crater is large enough to explain the extinction event by itself (unless you hew to the volcanic explanation, I suppose), so the question is whether there is any evidence for multiple impacts. As far as I know, the global distribution of the physical evidence is indicative of a single source, but not definitively so.
On a long enough timeline, improbable events are expected.