All of Israel are responsible for each other.
“There is a certain people scattered abroad and dispersed among the peoples.” (Notes in parentheses are mine) Haman (the main egoistic characteristic of the person, one of the manifestations of Pharaoh, Amalek, and so forth) said that in his view, we will succeed in destroying the Jews (destroying the connection between those who yearn for the Creator in a greater and more final form), because they are separated from one another; hence, our force (the egoistic power that drives us away from bestowal and love) against them will certainly prevail, as it causes separation (of those who yearn for the Creator) between man (of each one of them) and God. And the Creator will not help them anyway, since they (through distance from each other) are separated from Him. This is why Mordecai went (the characteristic of bestowal in a person) to correct that flaw (the characteristic of separation, the Haman in a person), as it is explained in the verse (in Megillat Esther): “the Jews gathered,” etc., “to gather themselves together, and to stand for their life.” This means that they had saved themselves by uniting (Connection with the Creator)
Writings of Baal HaSulam, Shamati #144 “There Is a Certain People”