meaning - Is there any nuance in ‘I was kind’ when it means ‘I treated her kindly”?

"But I was patient. I wrote back. I was sympathetic, I was kind. Ginny simply loved me. No one’s ever understood me like you, Tom …. I’m so glad I’ve got this diary to confide in …. It’s like having a friend I can carry around in my pocket …."
(p309, Harry Potter 2, US edition)

NB --
The speaker, Tom Riddle, is a villain in this story. He is boasting how well he could win Ginny’s heart by becoming a kind of pen pal with her.

The author describes his character as an impatient, unsympathetic, and unkind one. Therefore, I would think his saying expresses temporal action, not permanent character. He treated her kindly at that time and his attitudes got Ginny to fall in love.

But I feel something strange when ‘I was kind’ and ‘She loved me’ express action, for I’ve run into much more ‘be kind’ and ‘love’ which describe someone’s character or continuing state since I started studying English.

So, here is my question.
Is there any nuance in ‘I was kind’ when it means ‘I treated her kindly”?

In other words, why does the speaker use such expressions, instead of other expressions like ‘treat kindly’?

Answer

I voted-up Rofler's answer, so I will not repeat what he said, and with which I agree. Let me say that I think you are asking the right questions, since...

I was kind. /then/

on its own would, indeed, imply truthfulness, a sincere kindness; but still there are two sides to each coin and to life there are many sides, so the statement can be said also if you were kind only to a particular group or a person (and they can truthfully perceive you as kind), or only in particular period of time or a moment.

It does not imply that

I am kind. /now/

nor the above sentence implies that

I will be kind. /for ever and ever/

Maybe you would take it as better if it would have said:

I was patient. I wrote back. I pretended to be sympathetic, to be kind.

However, there is another trick at work here; this is written in first person and in the context of this character you already expect a different ethos, a different attitude towards truth.

If such character says

I was gentle.

you are not experiencing the same value of the message as when the exact same sentence is said by Nabokov's Lolita or Bulgakov's Woland.