In Three Men in a Boat, why did the narrator remember his Uncle Podger and what was the condition when he tried to hang the picture on the wall?

J., the narrator of Three Men in a Boat, tells a lengthy story about his Uncle Podger in Chapter III. Here is a man who thinks he knows how to do something -- maybe he thinks he knows how to do many things -- when in fact, he’s quite helpless and needs the assistance, verification, and admiration of everyone else around him to do the simplest task. The incident J. recalls is when his uncle once decided to hang a picture on the wall. The task only required the framed picture, a nail, a hammer, a step-ladder, and perhaps a pen or pencil to mark the spot where the nail should go. But Podger made a big deal of the challenge. He called on all of his family members to bring him the tools. Then he kept “losing” some of them. He dropped the picture and cut his finger on the glass. He hit his thumb with the hammer. And on and on the ordeal went; until near midnight, when the picture finally hung crookedly on the wall, the room was in a state of shambles, and Uncle Podger commended himself on a job well done. He had sapped the strength of everyone around him.