Here's my understanding of the issue. There are two plausible explanations of how Covid-19 became established in Wuhan, China.
1. Like other corona virus diseases that evolved in the wild from other species, Covid-19 evolved via transmission in the wild from the bat reservoir to other species including humans.
In the past two decades, the world has seen three coronaviruses emerge and cause outbreaks that have caused considerable global health consternation. Coron
academic.oup.com
2. Alternatively, covid-19 emerged from a respiratory disease seen in Chinese bat guano harvesters in 2019 or from similar outbreaks seen in prior years. Guano virus was under study in the Wuhan laboratory and may well have escaped the lab. China's lead scientist at the lab denies any outbreak or escape occurred, but it's reasonable to doubt whether Chinese authorities would allow someone in her position to tell an unpleasant truth.
Wuhan-based virologist Shi Zhengli has identified dozens of deadly SARS-like viruses in bat caves, and she warns there are more out there
www.scientificamerican.com
Certain extremist voices find it convenient to conflate theory #2 with the unsubstantiated notion that the Wuhan lab was engaged in secret military research to weaponize the respiratory illness via "gain of function" improvement, and that's what gave the world covid-19.
To be fair, even Rand Paul's website comes close to a fair statement of #2 despite tagging "gain of function"
"The amendment defines gain-of-function research as “any research project that may be reasonably anticipated to confer attributes to influenza, MERS, or SARS viruses such that the virus would have enhanced pathogenicity or transmissibility in mammals.” This is the same definition the NIH used when implementing a funding moratorium on gain-of-function research in 2014-2017.
"The origin of the COVID-19 virus is unknown. It has yet to be determined if the outbreak began through contact with infected animals or due to a laboratory accident at the Wuhan Institute of Virology in China. But this pandemic, and the questions of its origin, has exposed the inherent risk of gain-of-function research and never again will taxpayer dollars fund this type of research in China."
www.paul.senate.gov