The answer to this question can be found in Scene 8 of this delightful farce, and the discovery that Mrs. Popov reveals about her dead husband is rather incongruous given the way that she remains so true to her husband's dead memory, wearing mourning clothes and protesting that she will remain locked away in grief for the rest of her life. Note what she tells the irrascible Smirnov when provoked by him to tell him what she really knows about men:
If it comes to that, the best man I've ever known was my late husband, I may say. I loved him passionately, with all my heart as only an intelligent young woman can. I gave him my youth, my happiness, my life, my possessions. I lived only for him. I worshipped him as an idol. And--what do you think? This best of men was shamelessly deceiving me all along the line! After his death I found a drawer in his desk full of love letters, and when he was alive--oh, what a frightful memory!--he used to leave me on my own for weeks on end, he carried on with other girls before my very eyes, he was unfaithful to me, he spent my money like water, and he joked about my feelings for him.
So, in contrast to what we expect from Mrs. Popov's late husband, she reveals at this particular juncture in the play that her late husband was a terrible specimen of the male form, and that he was deliberately unfaithful and wasteful in spite of her great love for him that remained constant and true over the years of their marriage.