Ireland striker Keane returned to Tottenham on Monday after just half a season at Liverpool who paid £20 million for him and failed to buy a replacement in the transfer window.
"Sometimes good players cannot settle down in the team and when this happens you have to consider the situation and try to react quickly," Benitez told Liverpool's website.
"If it is not good for the team then it is better for everyone to make a decision and because of the situation in the transfer market and for the opportunity for the player we had to do it now."
Tottenham have not disclosed how much they paid for the 28-year-old Keane, although reports said Liverpool made a loss of at least four million pounds.
"I have to analyse things and try to look at the bigger picture and this means thinking of the club and the team and what is best for them," Benitez said.
Keane struggled to replicate the form he showed in six years at Tottenham, scoring seven goals in 28 appearances for Liverpool, but his hasty departure weakened Benitez's attacking options as the club chase a first league title since 1990.
Any more injuries to leading striker Fernando Torres, who has been plagued with hamstring problems this season, could call Benitez's judgement into question.
"We still have (Ryan) Babel, (David) Ngog and Dirk Kuyt as well as Torres. It is a risk but the situation was not good and we needed to do something," Benitez said.
"Now I would like to wish Robbie the best because although things did not work out he has been working hard for us.
"He was trying to do his best and the key was that Spurs showed a lot of interest and they were pushing really hard for him."
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