Why is it halibut fish consider a kosher food if they eat almost anything could fit in their mouth I am so curious of this type that means are scavenger?

Halibut is considered kosher not because of its diet, but because of its physical characteristics. Kosher fish must have scales and fins, and halibut has both. The fact that halibut are scavengers has no bearing on their kosher status.

There are many other species of fish that are considered kosher, even though they may eat a variety of things. For example, carp, catfish, and herring are all kosher, even though they all eat other fish, worms, and other creatures. The key factor is that they all have scales and fins.

In Judaism, the laws of kashrut are based on the Torah, which is the sacred text of Judaism. The Torah lists the animals that are kosher and those that are not. Halibut is listed as a kosher fish in the Torah.