Twitter leaders decided that the old bird was over-the-hill. And too fat. No more tubby, toddler-appropriate tiny "Ts," either. Logo refreshes aren't unusual, but they typically happen over decades, not months.
For example, take the evolution of the NBC logo (all the NBC logos below are the property of NBC):
Lightening Bolt logos - used 1931-1842. (The NBC Chimes were first heard on the radio in 1927.)
Microphone logo - used 1942-1953 Xylophone logo - used 1954-1959
Original Peacock logo - used 1956-1962 Original "snake" logo - used 1959-1975
"Laramie Peacock" logo - special uses 1962-1975 The "Fancy Cut N" logo - 1976-1979
"Proud N" logo - used 1979-1986 And finally, today's logo used since 1986
NBC has numerous variants you'll see, too - green for St. Patrick's Day, black/orange for Halloween, red/pink for Valentine's Day, the logo with a Santa hat for Christmas and donning a party hat to celebrate a New Year.
Imagine if law firms fussed with their logos in this way, making them holiday-appropriate - a brand stewardship challenge for sure.
For now, adios little fat Twitter bird, and a warm welcome to the younger chick.