Bands that musically "Jumped the Shark"?
But what bands have either,
1 - An established band changes their musical or lyrical style to coincide with current pop music trends to sell records.
2 - A band that gets a new member so that more focus can be made on that new member and so they can get more exposure, kind of like Arch Enemy when they got Angela Gossow
3 - A band that does something uncharacteristically out of the ordinary to start some hype or to get some lost appeal back, i.e Kiss unmasked
or you can also provide some other way a band drastically changed