Why am I misunderstanding freewill?
Let's cut to the chase. People make choices. These choices have various levels of constraint on them for a variety of reasons. This has nothing to do with free will in a religious context.
Free will in a religious context is whether human choices are controlled by God, or if certain choices such as a choice of a religious tradition or belief in God are unconstrained by God. For an atheist there are no choices constrained by God as there is no God. It is really that simple.
If you want more on constrained choices, all social animals have what passes for a conscience which is trained initially by mama smacking herm on the butt when hesh does something not permitted by the herd or society. As hesh gets older mentors and/or alphas take over from mama with increasing severe punishments up to exclusion from the herd or tribe which is in effect a death sentence quick or slow depending on the environment. Those who watch the fate of one "thrown to the wolves" very quickly internally constrain the behavior that led to the action.
None of this is really conscious behavior, either in training or accepting the constraints of the conscience. It is simply part of staying alive in the group. Humans and perhaps other animals have some conscious control over the dictates of conscience, and may choose to behave differently from the group if necessary or desirable. You may call this free will or intelligent choice, it makes no difference. The alpha says frog you may or may not choose to hop. But you know in some cases refusing to hop is to be thrown to the wolves. In some cases the wolves are a better choice. This is free will.
In a religious context if a major component of your self worthiness is defined as sin, say not believing in the local God or one of His stupid rules, the atheist wolves may be the only choice. We really aren't as scary as mama tol' ya we are, but for some religious people especially teens suicide is a reasonable alternative. Always talk to an atheist first.