What happens when we pass one invalid argument and valid argument to mvn command Eg mvn clean -DskipTests -DNgbuild where -DNgbuild is invalid argument and -DskipTests is valid argument

Question

I execute a command
"Mvn clean -DskipTests -DNgbuild" where "Ngbuild" argument is invalid but skip test is valid.
This command fails to skip test even though it's valid

But when I give "Mvn clean -DskipTests" it skips successfully skips test
Why so?