As for what Trump likely had in mind when he used the phrase "this Russia thing with Trump and Russia is a made-up story," later on he makes a remark, "I'm not talking about campaigns. I'm not talking about anything else. I'm not under investigation."
I don't know what is in your mind, what you are ascribing to Trump, with your "Trump says he was thinking about Russia," but I do know how I take Trump's remarks, viewing the interview in totality.
Uh, no, it's not. Here's the quote from the video:
"When I decided to do it, I said to myself, 'this Russia Trump thing is a made up story, an excuse by the Democrats for having lost an election'..."
Go back to 0:35 to see the "it' he's talking about is firing Comey. So unfortunately he did state when he decided to do it, he was thinking about the Russian investigation.
I do know how I take Trump's remarks, viewing the interview in totality.
His first part of the answer, that you originally quoted, was great. He should have left it at that.