FIA president Jean Todt believes a lack of unity caused Sebastian Vettel's time at Ferrari to ultimately end in disappointment.

Last week, it was confirmed the German would be leaving the Italian team at the end of this year, claiming in the statement there was no longer the "common desire" to continue.

While there is still 2020 to potentially achieve the ultimate goal of a Formula 1 title together, Vettel's dream of winning with Ferrari has been overshadowed by the dominance of Lewis Hamilton and Mercedes, errors at key times and, most recently, the emergence of Charles Leclerc.

And it is the apparent wish to promote the Monegasque into a lead driver role from next year that left 2009 world champion Jenson Button dumbfounded.

“If he [Vettel] was pushed, for me it’s madness,” he told Sky Sports.

“A four-time World Champion. I think he showed his speed last year. He had a tough moment in the season when Charles was performing really well and I think that hurt him a little bit mentally.

“But he came back really strong, and he’s just somebody you would definitely choose to put in your car if you had an F1 team.

“There must be more to it. I don’t know if Ferrari is going down the route of not wanting two number one drivers or what but it’s a really strange choice for me and I’m still shocked that Sebastian [won’t be] in a red car.”

For Todt though, he sees more to it than just Leclerc.

"The result, good or bad, you can always explain it," he told the UK broadcaster.

"Together with Michael, the whole team at Ferrari, we had so much success because we had a very united, strong team, who were supportive to each other, mainly in the difficult times than in the good times.

"It's easy to be together when all is good, but you see a good sailor in a rough sea. When we were in a rough sea, we were all on the boat, and I think that's what made the difference.”

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The former Ferrari boss though doesn't dispute Vettel's ability.

"Sebastian Vettel is one of the greatest talents in motorsport," Todt stated.

"An announcement has been done, he will not drive for his actual team beyond 2020. There are a lot of other opportunities.

"We can only wish him the best, and I really feel that whoever will take him, will be very lucky."

In the longer term, the Frenchman even tipped the 32-year-old for another key role.

"Maybe he will be a good president of the FIA in the future. You never know."