Why didn't Silva sign for Real Madrid?

Manchester City has been able to bring to light a documentary that covers David Silva's entire professional life and can be seen through 'City+'.
A part of the documentary focuses on Silva's beginnings, where they show the Canary Islands native was a step away from Real Madrid before starting his career in the elite in Spain.
The now City captain was only 12 years old when he went to the Real Madrid youth team facilities, looking to get the coaches and scouts' attention.
However, the transfer did not take place because of the lack of decision by Real Madrid, who failed to see his potential and let the 12-year old David Silva slip away. The now football legend both in England and in Spain could have had a very different career had he signed for Real Madrid's youth teams then.