Interpreting Villain's actions

vs a maniac (very LAG style), I will rarely call especially out of position. I prefer bet/raise or fold. I call mostly if I have monster hand to induce aggression. We must understand that variance will be higher because we will play many big pot.

And if I don't feel comfortable, I'll leave the table. Don't let your ego drive you.

Agreed.
Poker is like curing acne, "You must pick your spots carefully".

In this hand, it was a standard open raise.
I CBet the flop, because I would with pretty much any hands that I would open from EP. I considered a check/raise AI, but this way I control the betting.

On his 3Bet I shipped.

The hand itself was just meant as an example, though.

The question is:
Do players project their own attitudes on to other players?
In other words, when I shipped on his 3Bet post flop, did he interpret this as a stone-cold bluff, since that is what he himself would do?

He called the shove, and held KQo.

I don't think that ego enters the picture here, since I had played against him personally at that point only once, where I raised pre and folded on a totally missed flop.

I went back over the session and had a look again to see what he had been holding, and he had been raising people out of pots so much it was hard to find hands where his hold cards actually showed.

The question is: Do players project their own attitudes on to other players? In other words, when I shipped on his 3Bet post flop, did he interpret this as a stone-cold bluff, since that is what he himself would do?

yeah, I think so. But at a very specific spots.
I noticed that someone who like to overbet on the river tend to call my overbet wider. And someone who have high "3bet preflop" tend to call or 4bet my 3bet wider.

Remember that we might be misinterpret how is villain thinking. He could be:
1. 3bet bluff all missed cbet or
2. 3bet bluff all missed cbet with drawysh board or
3. 3bet bluff once every 5 minutes, etc.

And I'm talking about < NL10. Don't know about higher stake. I guess it do not apply at higher stake.