Why is it that bands second or third album take a bad direction?

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A+

Well, see, think about it. A band releases an album. They've written about twelve songs. Then they release another album, or maybe two more. By this time, they've written dozens of songs, all in the exact same style. It would be like an artist painting the same landscape every year. There might be little differences, but it's still the same landscape. Eventually, they'll get bored, and will want to move onto something new. To the fans who enjoyed the old style, the new one is probably going to seem terrible. An example would be Metallica. Their first four albums, and by a stretch, the fifth, are all very similar. After that, they got bored of the same old stuff, and began to experiment. Some people liked it, most hated it. Personally, I liked Load and Reload, but I will never hold them as high as Master of Puppets or Ride the Lightning. So anyway, bands are just like anyone else, they get bored, and want to try something new.

After their first couple of albums, bands tend to get bored with their sound and experiment in different musical directions. It's normal for a band to try a new sound as putting out several albums that sound too similar would lose fans' interest. It's a normal part of a band's life, like puberty is with teenagers.