How is the poem by Oliver Holmes ironic?

Oliver Wendell Holmes's poem, "The Deacon's Masterpiece; or The Wonderful 'One-Hoss Shay," is ironic because of the contrast between the Deacon's pride in his creation and the ultimate fate of the "wonderful one-hoss shay." The Deacon painstakingly builds the carriage with perfection and durability in mind, taking care to use only the best materials. However, his arrogance and overconfidence are revealed when the "wonderful one-hoss shay" suddenly and inexplicably collapses after 100 years and with "no damage done" despite its apparent lack of defects. This unexpected outcome stands in stark contrast to the Deacon's initial boasts and highlights the unpredictable and often contradictory nature of human endeavors and the fallibility of even the most meticulously crafted plans.