Presumably because the official case was archived for lack of evidence?
Remind us:
When was Dr Amaral removed from the case? I presume it is he to whom you refer as "the original lead detective"
What was the date the case was archived?
What was the date of publication of Dr Amarals book?
"Presumably because the official case was archived for lack of evidence?" ... Hmm, and as we have seen subsequently there was a wealth of suspects and witnesses who it seems did not fit Dr Amaral's theory.
Cursory questioning at the time (with perhaps the exception of Malinka and Murat) allowed whatever evidence which may have been available to solve Madeleine McCann's case in 2007 ... only being looked at in 2014.
Unfortunately the original chief investigator developed his theory immediately (check his book) and ignored all other avenues of investigation or evidence in pursuit of that theory (Paiva 2010).
Monumental mistakes in any inquiry ... but particularly reprehensible when a missing child is involved.
I'm sure if you 'google' for the date of Dr Amaral's sacking, the archiving of Madeleine's case and the date of the publication of Dr Amaral's book you will find the answers.