Joseph,
they did not ask to the extra day in shushan to “finish the job” there was no way they were going to finish the job,nor did they “finish the job”
R’ Y. Eiybushitz says that esther asked for the extra day to show the yidden that this was not teva. and that this was all due to HKBH. Teva would just turn Haman’s day into Esther’s day, the extra day shows HKBH calling the shots
R’ Brevda says that the extra day was done to disprove those who might say this was all in the mazalos, and that Haman got it wrong. The extra day shows that it wasn’t that Haman misread the stars, rather Hashem had a different plan