Two trophies and qualification for the second round of the Champions League simply weren't enough to keep his demanding boss Massimo Moratti -- the Inter president -- happy.
And filling the boots left by Jose Mourinho simply proved beyond the Spaniard's capabilities as his unhappy tenure in Italy suffered a quick death.
Whether or not Moratti and Inter have taken the right decision remains to be seen but the feeling amongst many people is that Benitez had accepted a poisoned chalice.
Bayern Munich coach Louis van Gaal intimated as much ahead of his team's visit to Roma in late November when he said that part of Mourinho's reason for leaving the Italians after just two years in charge was because he would never be able to emulate his early achievements.
Mourinho won Serie A in his first season and followed that up with the first ever treble in Italian football in his second year, landing the Italian league, cup and Champions League.
It was the greatest season in Inter's proud history and their first success in Europe's premier club competition in 45 years.
Mourinho had achieved everything he was brought to the club to do and he walked out as the Messiah, an eternal hero to Inter fans whose place could never be taken.
Benitez, who enjoyed great success with Valencia and then followed that up with an achievement of sorts at Liverpool, walked into the great void vacated by Mourinho with a near impossible task ahead of him.
In a way it was tantamount to the task facing the man who one day replaces the incomparable Sir Alex Ferguson at Manchester United -- although Mourinho has already made it clear that he would relish such a challenge.
And that task was made all the more complicated by the fact that he did so in a post-World Cup year, when most of Inter's players would be suffering not only a success hangover but also from the effects of an extended summer's work.
That Benitez failed, in a way, is more indicative of the unforgiving nature of football management, especially in Italy, than his own shortcomings.
Not only were his players fatigued from their previous exertions but Benitez was also soon faced with an injury crisis that would have challenged any coach at any team.
And whereas Mourinho was unequivocally backed in his transfer dealings, Benitez was given nothing.
Mourinho asked for a defensive midfielder and two wide players when he arrived at Inter in 2008, being given Muntari Sulley, Ricardo Quaresma and Mancini.
And even though his wide men proved to be flops while Muntari had lost his starting berth by Mourinho's second season in charge, so he requested further reinforcements and was given Diego Milito, Samuel Eto'o (in exchange for the departed Zlatan Ibrahimovic), Thiago Motta, Lucio and then also Goran Pandev.
Milito, Motta and Pandev spent much of Benitez's time in the treatment room, as did Walter Samuel, Esteban Cambiasso and Julio Cesar, while Mario Balotelli was sold and not replaced.
Even indestructable captain Javer Zanetti spent his first period in years on the sidelines.
Inter's form was patchy at best despite winning both the Italian Supercup and Club World Cup, ending the year in seventh in Serie A and finishing second to Tottenham in their Champions League group.
But by then Moratti had become used to success and the man who fired Roberto Mancini after three straight Serie A titles lost patience with Benitez.
His successor's task will be no easier but at least he won't be burdened by having to follow Mourinho, instead he'll be following the perceived flop that was Benitez.