Himanshu had to opt out because of channel where he is playing Lord Shiva..
Here is article of why he can't play Krishnaji..
It seems like the broadcasters are mightier than the Gods on TV. How else does one explain the overnight backing out of Himanshu Soni, who was finalised to play Lord Krishna in Siddharth Kumar Tewary's Suryaputra Karn? Here is what happened " Himanshu, currently seen as Shivaye (an avatar of Lord Shiva) in Neeli Chatri Wale, was roped in to play Lord Krishna in the mythological show Karn on a rival channel. While the actor was excited about the new venture, the channel airing Neeli Chatri Wale pulled the plug on it. "The channel objected to him taking up the role of another God on another GEC (General Entertainment Channel). This sudden development sent the makers of Karn in a tizzy as they had to burn the midnight oil to hunt for a replacement." Says Himanshu, "I am already playing God in another daily and so was no allowed. I had no choice but to opt out of it. I could have managed both the shows, simultaneously."
Krishna's role has now gone to actor Saurabh Pandey, who was seen in the same production house's Razia Sultan. He says, "I am playing a God's character for the first time. I am a Krishna-bhakt and to portray Him is very difficult. Call it a coincidence or divine intervention as I bagged the role two days after my first visit to Vrindavan."
