M’nos HaLevi writes that the verse mentions that Mordechai does all of these actions to demonstrate Mordechai’s enthusiasm to be involved in every part of the mitzvah of saving the Jews. When great leaders in our history get involved in a mitzvah, they put all of their energies into the project. R’ Moshe Feinstein often had to let down organizations by saying he could not be on their boards because he was not content to be a figurehead – he used his priceless time and abilities to be involved in every aspect of the operations, including planning, payroll, bookkeeping, organizing, and even decorating.
One may wonder if this goes counter to the idea of zrisus (“alacrity”). After all, perhaps if Mordechai had delegated some responsibilities, Jewish lives would have been saved sooner. In Alei Shor, R’ Shlomo Wolbe explains that zrisus does not always mean doing things quickly; rather, it can mean doing things efficiently, properly, and with care.