Trump is not stupid. He has to assume that everything he says is being heard by an unintended recipient. This has been an ongoing issue for all presidents for decades.

The White House phones, the physical phone lines, were tapped back in the mid-90s when Clinton was president. The Israelis built and installed the phone system for the White House via a contract with a US based company. The Israeli built system had built-in ability to allow them to listen in real time to all White House phone calls.

Part of the electronics for the system were installed in a building that I worked in... 20 feet away from my office and just a few miles from the White House. I worked for a Private consulting firm specializing in national security issues and owned by a former Israeli intelligence chief. That is how I know.

They caught an unauthorized person in the telecommunications room one day (this was the room 20'feet away from my office) and all hell broke loose. The guy was able to flee. He left his equipment that he was using for whatever he wasn't supposed to be there for. Crazy day.

Anyway... they told Clinton not to use the phones for national security purposes so he called Monica lewinsky. No joke.