The Houston Rockets selected Jalen Green with the number two overall pick. A year after, the franchise was forced to trade away the second-best player in franchise history. James Harden and the Rockets parted ways during the 2020-21 season. Plenty of franchises have lost their franchise player.
The Cleveland Cavaliers lost LeBron James twice, Kevin Durant is on his third team, and the aforementioned Harden forced his way from his second team in a year. It happens regularly as players are starting to take their future into their hands.
Many of those teams that lost their franchise player struggle for years to find a replacement, if at all (see Lakers after Kobe Bryant retired).