A liberal means someone who thinks that they can use the system that is in place, no matter how broken it might be, and make slow gradually progress to help society. However, corporate power and others with extreme far right ideologies have used this desire to use a broken system more as a means of control, exploiting mechanisms like the Overton window and political division. A liberal therefore is often trying to get more right leaning bipartisan support to compromise in the hopes it will eventually lead to change while alienating their base how is actively being hurt.

To put it another way, a liberal is someone who will watch their friend get punched in the face and then try to help buy the attacker boxing gloves.

I don’t know where this idea of a radical liberal came from, a radical is the literal opposite of a liberal. I guess it’s just a natural misunderstanding that can happen in a society where the actual left is criminalized, and the closest thing to the left is a liberal party to the right of center.