He told this as a mashal of people who run after dead things. They live for seventy or eighty years, run after dead things, like money and pleasures, and don't pursue "live" things, such as Torah and mitzvos. They end up with their dead merchandise, while the live matters fly away and elude them.
The same applies to Purim. Some people run after dead things on Purim and become absorbed in trivial matters. Minor matters occupy their minds. But there are live things to achieve on Purim (such as simchah, deveikus, praise to Hashem, mitzvos, etc.). Pursue what is alive, and don't get tied down by what is dead.
The Tur (693) writes, “Rav Amram z’l writes... to say extra tefillos on Purim since it is a day of miracles (נס יום). We were redeemed from our troubles on this day. Therefore, we must ask compassion from Hashem to redeem us once again.”
The Imrei Noam writes, התגברות יש פורים בימי מראש למעלה עד והרצון הרחמים, “On the days of Purim, compassion, and love abound to the highest degrees.” Notice that the Imrei Noam writes פורים ימי, the two days of Purim. This is because Shushan Purim is also a day for tefillah.
The Ateres Tzvi zt’l taught that a person could accomplish more with his tefillos on Shushan Purim than on Purim.
The Miracle Came from Tefillah
The Midrash (Esther Rabba 7:13) states, "When Haman plotted to destroy the Jewish nation, Eliyah HaNavi z'l ran, in a בהלה, confusion, to the avos (Avraham, Yitzchak, and Yaakov) and to Moshe Rabbeinu, and he said, 'Holy forefathers! For how long will you sleep in your graves? Why aren't you paying attention to the tzarah the Yidden are in? The malachim, the sun, moon, and the stars are all crying bitterly, and you are keeping distant and not paying attention.'
"The avos asked, 'What is the reason for this decree?'
"Eliyahu replied, 'Bnei Yisroel ate at Achashveirosh's party, and it was therefore decreed that they will be destroyed and that their memory be erased forever.'
"The avos replied, 'If they transgressed Hakadosh Baruch Hu's laws and therefore the decree was signed, what can we do about it?'
"Eliyahu returned to Moshe Rabbeinu and said, 'Devoted shepherd of Bnei Yisrael. Many times, the Jewish people's lives were in danger, and you prayed for them. You annulled the decree, and the nation was spared. [Now, once again, daven for the Jewish people.]'
"Moshe replied, 'Is there a tzaddik in the generation?'
"Eliyahu replied, 'There is. His name is Mordechai.'
"Moshe said, 'Tell him about the decree. He will daven that the decree should be annulled from the earth, and you and I will daven before Hakadosh Baruch Hu in heaven.'
"Eliyahu said, 'But the decree has already been written.'
"Moshe said, 'If the decree was sealed with clay, our tefillos could be effective. If the decree was sealed in blood, what will be will be.'
"Eliyahu replied that the decree was signed in clay."
Moshe repeated, 'Tell Mordechai about the decree.'
"Eliyahu went to Mordechai and told him. As it states (Esther 4:1) אשר כל את ידע ומרדכי בגדיו את מרדכי ויקרע נעשה, 'Mordechai knew everything that happened and Mordechai ripped his clothing.'..." He knew about the decree because Eliyahu told him about it. Moshe and Eliyahu davened in heaven,
