Why not. If he can’t make a promise for Congress, then why did he make, on numerous occasions, promises for Congress?
Because he was a political candidate running for office, and political candidates promise the voters whatever he thinks they want.
Here's how a very brief conversation between the President and Congress might go:
Trump: "We have to fund the border wall because that's what I promised during my campaign."
Congress: "WE didn't promise that to anyone. If you want a border wall, go build it yourself and call it the Great Wall of Trump."