Oracle cannot connect to SQL developer as sys account
sqlplus user/password as sysdba uses OS authentication by default, and bypasses the username and password check, so as you said, you can provide any password or username.

Logging in from SQL Developer requires a remote session. For a remote SYSDBA connection, you need the following:


set remote_login_passwordfile to EXCLUSIVE or SHARED, but not NONE
create a password file for the database if it doesn't already exist:


$ orapwd file=$ORACLE_HOME/dbs/orapw$ORACLE_SID

After this you should be able to log in with SYS and the password you provided.