With the T6 hand, it's pretty clear the other guy was not playing T high on an AA8 board but was playing the other player.
Perhaps he had noticed a tendency to be overaggressive by the other guy so decided to push him off his hand at some point, knowing that the guy would have a wide range. Given the other guy's holding it seems if this was his reasoning he was correct.
When he hits his miracle runner runner, he has no need to push the guy off his hand so decides to let him just bluff the pot on the river. He got his read spot on as the guy was very un likely to call a bet on the river with 44 so he gave him a chance to bluff.
It's not ABC poker but it's good to deviate from standard plays every so often and the best players are accumulating chips with these sorts of plays while every else is waiting for big hands.
Bear in mind also that when he showdowns this hand, everyone looks at him and mentally says "unpredicatable." People will be scared of calling his raises/ reraising him without monsters as they won't know what he has and I bet no one went after his big blind after this for similar reasons. These metagame aspects add to the value of the move.
The second hand isn't so bad either as there are two obvious draws in the flush and the straight and there's enough in the pot that's it's worth stealing with a semi-bluff/ draw (which is how he might have read you) and it's worth taking down with top pair so his play isn't too bad. He is also left with a workable stack when he is wrong.
