The word that best completes the sentence is "fanatical."
In this context, "fanatical" describes fans who are passionate and enthusiastic to an extreme degree, often spending a lot of time and money to support their team.
The other options don't fit the context as well:
- "Fatuous" means silly or foolish, which doesn't convey the same level of dedication.
- "Flagrant" means something that is shockingly noticeable or obviously bad, which doesn't apply here.
- "Feline" relates to cats and would not make sense in this context.
So, the completed sentence would be: "Some of the team's fans were fanatical and spent incredible amounts of time and money following them around the country."