This is because the pieces of the sharp singularize $\Theta$. Let $s_n$ be the sequence of the first $n$ cardinals above continuum and let $a_n$ be the $n$th cardinal above continuum. Then the theory of reals with a parameter $s_n$ in $L_{a_n+1}(\mathbb R)$ is a set of reals $A_n$. They are Wadge cofinal in $\Theta$, another words the sequence $\langle A_n: n<\omega\rangle$ is not in $L(\mathbb R)$ but each $A_n$ is and that is why you get a singularization.