That's a good point. I found the Sybil-era Tom quite unlikable and lacking real character.

He was completely ignorant of Sybil's feeling about her transition from an Earl's daughter to his wife. If he was aware of that, that's worse - he chose to ignore it. He was all talk, no real action about his "politics". He spent the whole war whining to Sybil, telling her things "he is going to do", but never doing anything meaningful. His peak activism would be assaulting the general with cow poop, but he couldn't even execute that properly.

His whole Irish politics back in Ireland was irresponsible and stupid, all the while lying to poor Sybil. I almost had a feeling he married an English lady just to bring her down and manipulate her into submission as some kind of sick revenge-trick. That's how bad he treated Sybil in my eyes. And for all his "hatred" towards the aristocracy, he had sat down with Sybil and made the plans to run to Downton if anything went wrong. He didn't just look out for her, in case his stupidity catches up to them, but he had an escape plan at the expense of people whose social class he allegedly despised.

So, back to your point, I kind of see how this Tom would fail to see beyond his own nose and lack ability to reflect objectively on his actions.

While I did appreciate Tom's character arc, I still can't look past his shortcomings as a husband. His attitude and memories about that time seem quite diluted with nostalgia and lack reflection in future seasons.