Which could explain his recent behavior.

Some can also become more vicious, which is often considered an unchildlike characteristic.

She thought she still lived with her parents and needed to call them to tell them where she was. She had a doll she kept by her side and talked to it all the time. No way could she grasp that I was her daughter, but she loved stories and songs. I got to enjoy the child within. As an adult mother she could be rather cold so it was a huge change.
My grandmother had dementia as well. She also became rather child-like, but both women had anger bouts in the earlier stages.
How would we know with Trump?

He also has (what he thinks) is a "tough guy" voice. I notice that Colbert uses it sometimes. Just a few things I've noticed.

Can you think of an example that I could look up and listen to?

He's often been petulant, but I haven't noticed a change in voice.

whole family. Family had to hides knives etc and locked all their bedroom doors to be safe.

There's a high degree of behavioral variability.

And he is less coherent than ever. Is it dementia or simply a mentally ill man under outstanding pressure of the hardest job on Earth?

I am an RN working with this population daily. Sometimes they become oppositional-defiant, sometimes they dont feel safe unless they are holding your hand to lead them places. Sometimes they become non-verbal and impulsive. But they all devolve to child-like states.

Although she barely knew my dad anymore, we figure she was in a comfortable place in her life.

of the night and call the police on her son and me, accusing him of stealing her money and holding her while I slapped her! Yeah, multiple times. The police had documented her status, but still had to come out.

She called me often with tales of shifty activity happening at night around the assisted living facility. Secret rooms being built. She claimed my brother was stealing money from her checking account (he had POA to pay her few bills.) The movie, "End of Days," scared the bejesus out of her. She thought it was real.

I think trump is becoming more delusional, and less inhibited, all the time. Mr. Bayard's mom became pretty beligerent, when she had always previously been this quiet, reserved lady. She would curse his dad relentlessly. It was shocking.

of anything nice anyone would do for her.

In other words, she became more of her true self. She could no longer obscure (that is, compensate for) her true personality.

... although not necessarily to childlike behavior. At one point he thought he was still on the farm and wanted to go out and milk the cows. This was in the late 1980s. He hadn't lived on a farm since leaving Finland for the US in 1917.