I worked for two companies as a lead and the first thing I did to make things better is - nothing. I asked questions and understand the why.
But what company have you worked for that you only have to understand code? There is code, underlying architecture, dependencies between teams, database schemas and the politics?
I also never said anything about only understanding code. I explicitly mentioned politics. But understanding your particular companies politics isn't necessarily helpful, probably because the politics are shit. So, if you go from one toxic company to another company, you might make it more toxic.
Junior people also tend to have the humility to know they’re inexperienced and lacking insight, so they tend to be more willing to “follow” the senior employees rather than attempt to leave their mark as a leader. “Too many cooks in the kitchen” and all that jazz.