I don't think he was neutered. I don't know what happened, but it's obvious his final days in office were a disappointment to his base.

If I had to guess, I'd say he gave it all he had and his final attempt was the 6th, having Pence send the votes back to the states and having a million patriots outside the capitol providing pressure on Congress to do so.

Once this failed, perhaps he just said "fuck it, I've done everything in my power, it's over". You can't rule this out as a possibility. I consider it the most likely of possibilities, even if it's not what we want to hear.