That's known only to Maharaj and the viewers who saw the scene.
No one else saw or witnessed it. Even Dhruv himself doesn't know that the King landed a blow on his attacker.
The problem from T's point of view is that there are three damning evidences against Dhruv, all of which she witnessed with her own eyes.
1) She saw "Dhruv" walk towards the chamber (in the same dress)
2) Her own father named Dhruv as his killer in his dying moments (folks generally don't lie then)
3) Dhruv took the knife out of her father's body.
In the absence of any other information, it's tough to come to a conclusion other than the fact that Dhruv indeed did do it. And there's enough technical "motivation" (the revenge for his father part)
Yes, her heart may say no after hearing the Dhruv saved the Kingdom news, but in the 17th century, there's an equal chance that folks could've done both X and Y (case in example Rajpurohit- who practically orchestrated the whole Samrat plan, but was also willing to die when Vikramjit asked him to perform D-PSM marriage)
I absolutely agree with this and this the only reason I am not completely off Tara. We know as viewers but in the show the characters do not.
I also think that they may have thought him being capable of this as prior to his anger he had come off as a very sorted guy and maybe that’s why they assumed that they can talk to him and he will understand. They never expected this level of anger. When Dhruv calmed down and read the letter he repented and agreed that Tara’s intentions were not bad and in Dhruvs fashion went to apologise. I am sure had they spoken at that time there was no way Tara would have even thought Dhruv was guilty no matter what daddy said. She doesn’t know Dhruv had a change of heart. Right before she left him he said love was not the same and what would she do if he hurts her dad?
I would like to see the story from her pov as right now we all know Dhruv and his thought but Tara is still a mystery. She was clear with her brother’s surgery but after that I don’t know what Tara wants or stands for.