2018 was also the year that Trump got rid of about 30 useless, possibly criminal Republican congressmen through "deciding not to run again". All Trump cared about was the Senate. I also tend to think that Trump wanted to give the House to the Democrats so they could make a tee-total ass of themselves -- which they did.
Yup.
As long as the House and Senate were not the same party, nothing would get done.
Also, the Senate is more important. They are the ones that approve the judicial appointments.