Was that agreement really signed on April 24th, or are they just using a standard court form whose latest revision was created on April 24th?
https://www.lawfareblog.com/document-michael-cohen-plea-agreement
Look for yourself. It is a standard letter format, not a form. The “Rev. 04.24.2018” appears in the footer of each page. It might be a “form date”, that really doesn’t make much sense since there is no “form” to date. It was signed and dated “8/21/18” by Cohen and his lawyer Guy Petrillo, (NOT Lanny Davis!!).
My conclusion is that Cohen agreed to this back in April and part of the deal was to sign and announce it when the Deep State thought it would be most to their advantage.