CFIT relates distraction to crashes. We lack a similar term in basketball, but good teams implode. Why? Reframe this into "what distractions and decisions create disaster?"
Coaching changes. Chuck Fairbanks transformed the Patriots from also-rans into contenders. During the 1978 season, he accepted the Colorado coaching job and the Patriots lost in the first round of the playoffs with Fairbanks suspended. Some consider the 1976 Patriots team the most talented in franchise history.
The Raiders won the Super Bowl that year, but the Patriots hammered them 48-17 during the regular season. The Raiders beat the Patriots in the playoffs abetted by several controversial officiating calls. History may not have repeated itself but rhymed as Bill Parcells defected in the 1996 postseason with the Patriots losing in the Super Bowl.
Underachievement. The Celtics upset the Cavs in the 2010 Eastern finals, 4-2, after the Cavaliers had a sparkling 61-21 regular season. LeBron was mortal, shooting 44.7% from the field, 27% from three, and 74% from the line in the series. To be fair, the surrounding cast (Shaq, age 37, Antawn Jamison, age 33) wasn't championship caliber.
Mistakes in judgment. The classic poor decision was Chris Webber's timeout call in the 1993 NCAA championship.
Fewer people remember the missed travel call leading up to the timeout.
Len Bias' cocaine death in 1986 forever changed the fate of the Boston Celtics. The second choice in the NBA draft was joining the powerhouse of Bird, McHale, and Parish...almost certain to extend their careers and possibly give them additional championship opportunities...never happened.
Relationship failures. I knew a strong high school team headed into a basketball postseason. A player on the team began dating a teammate's 'significant other' just before the playoffs. The team fractured and lost in the first round.
Questionable coaching decisions. The Spurs, up 3-2 in the 2013 Finals, led the Heat 94-89 with 28 seconds left. Tim Duncan was substituted out of the game twice in those fateful moments, missing two critical defensive possessions. Some consider this game the biggest blemish on Gregg Popovich's majestic career. The Heat tied the game in regulation and won in OT.
Officiating. Officiating, at every level, presents challenges. From player inconsistency (youth) to speed of the game (higher levels), officials get criticized. But rarely, officials go off the rails. Tim Donaghy claimed officials received instructions from the league and he bet on games he officiated. He plead guilty to corruption charges. "The revelation that Donaghy had been betting on games for four years — against league regulations — underscores the N.B.A.’s inability to detect such conduct."
And there's robbery.
The unifying themes behind these CFIT episodes were leadership failures, varying from organizational, coaching, and individual choice. I'm sure that you can find many more examples from your experience.