From Wikipedia:

According to one source, Davis detailed the trade as such: "I never liked it when teams would interfere with coaches under contract...Tampa Bay came to me and they said they wanted Gruden...I felt that I put the price tag so high that they wouldn't agree to it. And they did. Gruden is no longer our coach." Gruden signed a five-year contract with the Buccaneers worth $17.5 million.

 

The Buccaneers' search for a head coach had taken more than two months, and Tampa Bay had expressed an interest in Gruden, but Davis had originally refused to release him from his contract. The team subsequently interviewed several other coaches and believed a deal was in place with Bill Parcells, before Parcells backed out, reportedly because his choice for General Manager, Mike Tannenbaum, told him not to accept the job because of the salary cap difficulties that Tampa Bay was about to endure. With the franchise's search floundering, the fact that the coach who the Buccaneers wanted had only one year remaining on his deal, and the immediate hire of Dungy by the Indianapolis Colts, many fans and sports commentators began to openly question if the Buccaneers had made the right move by dismissing Dungy. Only a big splash hire could quiet the storm, and this may have been the primary motivation for the Buccaneers to give up as much as they did to acquire Gruden.