The word that best completes the sentence is "fanatical." The sentence would read: "Some of the team's fans were fanatical and spent incredible amounts of time and money following them around the country."
"Fanatical" describes people who are extremely enthusiastic or obsessive about something, which fits well with the context of devoted fans spending considerable resources on their support for the team.
The other options do not fit the context as well:
- "feline" refers to cats, and does not relate to fans.
- "fatuous" means silly or foolish, which doesn’t quite capture the intense commitment of the fans.
- "flagrant" typically describes something very bad or obvious, especially in terms of wrongdoing, which doesn't fit here either.