Why kattappa killed bahubali

"The saddest part about betrayal is that it never comes from your enemies."- Anonymous
The quote above might ring a bell to the people who recently watched 'Bahubali', the antecedent of the two part epic fantasy film that released this July. The movie is about the rivalry between two brothers, by the end of which Kattappa, the trusted royal commander unveils a shocking event from the past that not only surprises the audience but also leaves them inquisitive.
The movie, directed by S. S. Rajamouli has an amazing cast that includes Prabhas (Bahubali / Shivulu), Rana Daggubati (Bhalladeva), Tamannaah (Avantika), Anushka Shetty (Devasena), Ramya Krishnan (Sivagami), Sathyaraj (Kattappa), etc. in it.
Though the second part of the movie will be released only next year, here are five possible reasons as to why he might have done the heinous act.

Balladeva's trick

After Bahubali falls in love with Devasena, he gives up the throne in order to lead a peaceful life with her. Once Balladeva ascends the throne, there is war waged against Makizhmathi by the neighboring province. In the war, Bahubali is just a warrior and Kattappa is the war commander who has to obey a specific protocol given by the king. As the war begins, Bahubali refuses to kill innocent people and convinces Kattappa to capture the women and children without hurting them. But a special troop with the Makizhmathi banner kills the captives which compels Bahubali to fight against them. Meanwhile, Kattappa is tricked by Bhalladeva, who gives a war protocol saying that the Makizhmathi troop has a traitor in it and that he can be recognised as the one killing his own men. Kattappa is then ordered to backstab the traitor. Thus Kattappa would have been tricked into backstabbing Bahubali.

Vow made by ancestors

Kattappa might have obeyed the orders of the Bhalladeva as his ancestors had taken a vow to obey the orders of the Makizhmathi king. Without Kattappa, the army chief as an exception, his ancestors and the generations to come were forced to obey the pledge taken. Hence, Kattappa killed Bahubali adhering to Bhalladeva, the king's orders, as per the ancestral custom.
To save his daughter, Devasena.
Devasena might be Kattappa's daughter, whom Bhalladeva and Bahubali are attracted to. But her outright rejection to Bhalladeva and her growing affection towards Bahubali might have made Bhalladeva take Devasena as his captive and therefore blackmail Kattappa to kill Bahubali in order to save his daughter. Kattappa does what he is asked to but after Bahubali's death, he is ordered not to free Devasena. When Kattappa tries helping Devasena by going against his ancestor's vow, she refuses it, as she knows that Kattappa killed her husband and she pledges to be helped only by her son.

Blame game

In the film, there is a conversation between Bhalladeva and Devasena wherein he tells Devasena, that both of them are waiting for Bahubali to return as she has to see her son one last time and because he has to kill him once again with his hands.
This might imply that Bhalladeva might have killed Bahubali but Kattappa takes the blame as he is told to do so. Kattapa accepts the lie.

The Director's choices

Last but not the least, Kattappa might have killed Bahubali simply because S. S. Rajamouli’s script needed it. The whole idea of getting the loyal commander to look like a traitor might be an attempt to increase the curiosity of the audience. Thus, even after two months of release, 'The reasons why Kattappa killed Bahubali' seems to be one of the most discussed topics amongst the Indian audience.
So let us wait for the second part of Bahubali to clear the underlying suspense which might prove, Kattappa to be a victim of circumstances or otherwise.