The info in the link I posted into the research by Dr J Latham (a virologist) and Allison Wilson, PhD - is very helpful in showing how the virus could have developed rapidly to Covid-19, and why the virus did not emerge before 2019 is also addressed as is the involvement of WuHan Institute of Virology / WIV and Professor Shi.Are you saying RaTG13 is the precursor virus to sars-cov-2? It has been suggested that there is decades of natural evolution between the two so this scenario seems unlikely.
I will copy and paste in a separate answer - the start of a big section from their paper headed
Jonathan Latham, PhD and Allison Wilson, PhD
You can continue reading the rest in post with the peer reviewed links . The Q&A is also very good
The medical details were published in a 2013/2014 MA thesis (later a Phd) by the hospital Dr - Dr Xu
In April/May 2012 Dr Xu had 6 patients, who worked in the bat cave where the RaTG13 virus was later found. 3 patients died. This was initially treated as a potential SARS outbreak and hospital emergency.
Dr Xu's thesis links the miners deaths to an unknown SARS like bat virus from the caves. Some miners did test positive for a coronavirus and the ultimate conclusion of the thesis reads “the unknown virus [that] led to severe pneumonia could be: The SARS-like-CoV from the Chinese rufous horseshoe bat.”