Can a person just drive to the Grand Canyon and view it without having to pay for a tour?

We went there without paying for a tour, but we did pay to get into the park.

Unless you go on one of the six entrance free days or have a parks pass, you have to pay to get into the park. You don't have to take a tour though.

We don't know "where" you just pulled up.

West Rim of the Grand Canyon is on American Indian land and you cannot see it without paying an entrance fee.

South Rim there is usually an entrance fee but maybe maybe the entrance wasn't monitored at 1:30am.  There are places that the parking lot is directly on the rim. 

The area surrounding the actual park is huge.  You can pretty much drive in any direction and see amazing views.  There are roads with roadside stops, such as Native American jewelry and pottery, and other crafts.  There is one in particular that used to have quite a few vendors, and when you walk towards the back, the views were insane. I can't remember quite where it was, but not too far from the canyon.  Also, the park fee isn't that expensive.  The vehicle permit cost right now for the south rim is $35, which gets all of you in the park.  Be sure to check online at the CG website for any possible changes in regards to covid.

The Grand Canyon is a National park. You can find all info in it here

https://www.nps.gov/grca/index.htm

Tours are optional. Right now tours are suspended and can only be done virtually.  

Not all areas are accessible by car. 

Most visitor go to the South Rim which is open 24/7.  (Unless the pandemic has limited that) 

Many areas are not lit up. So walking around at 1 in the morning you are not going to be seeing anything and it can be dangerous. Many of their camp grounds amd trials are closed for winter or due to the pandemic 

You don't need a tour.  What you can do and see there depends on where exactly you are.  The Grand Canyon is huge and there are many viewing points with different things to see and do at each one.  You might just have nice views, but there may be other things nearby.  You do have to pay per vehicle to enter the official area of the Grand Canyon National Park; but you can view the canyon itself from other areas that are outside the park.