We don't know much about the real reasons obviously, most of what everyone says is honestly likely rubbish. But we can draw a lot of assumptions. Like they wanted to uphold their commitment to the pre-order crowd and feared the backlash of delaying, they wanted to be a part of the next-gen console launches, they feared blowback from the shareholders if it were delayed, they were so greedy they didn't care if it hurt them as long as they covered the development cost. Maybe they have plans to build new projects and didn't want to keep Cyberpunk lingering and holding back the studio for too long, maybe they had commitments to third parties collaborators about launching in 2020.
If I had to guess, a lot of it comes down to the console port delays. Apparently, the game was done on PC in early 2020 and it was delayed because they couldn't get it to run on consoles. I assume the higher-ups, after the delay and struggle with the consoles, assumed a position that it will take too long to fix the console versions and that they are committed to release and take the blowback from the console versions no matter what. They just didn't foresee how big the blowback was going to be.