Why are bats the source of dangerous coronavirus pandemics?
The preponderance of links between bat and human pathogens has led to a debate about whether bats disproportionately contribute to emerging viral infections crossing the species barrier into humans (26–30). Given the diversity of the Chiroptera order (Figure ​(Figure1),1), we may simply see more bat viruses because there are so many (>1,300) species of bats (31). However, even when accounting for the fact that they make up ~20% of extant terrestrial mammals, bats are overrepresented as reservoir hosts of pathogens with a high potential for spilling into human populations (32, 33). In fact, no known predictors that have been described to impact the likelihood of crossing the species barrier, including reservoir host ecology, phylogenetic relatedness to humans or frequency of reservoir-human contact, explain this pattern (32). Thus, why bats are such a frequent source of pathogenic human viruses remains a tantalizing mystery.


--Going to Bat(s) for Studies of Disease Tolerance

Other references that debate whether bats are special, generally conclude that they might somehow be, and argue about causes, include


Brook CE, Dobson AP. Bats as ‘special’ reservoirs for emerging zoonotic pathogens. Trends Microbiol. (2015) 23:172–80. This may be the best of the group, going into more detail and including more recent data
Dobson AP. Virology. What links bats to emerging infectious diseases? Science (2005) 310:628–9. 
Wang LF, Walker PJ, Poon LL. Mass extinctions, biodiversity and mitochondrial function: are bats ‘special’ as reservoirs for emerging viruses? Curr Opin Virol. (2011) 1:649–57. 
Olival K, Epstein JH, Wang LF, Field HE, Daszak P. Are bats exceptional viral reservoirs? In: Aguirre AA, Ostfeld R, Daszak P, editors. editors. New Directions in Conservation Medicine. Oxford, UK: Oxford University Press; (2012). p. 195–212. 
Luis AD, Hayman DT, O'Shea TJ, Cryan PM, Gilbert AT, Pulliam JR, et al. . A comparison of bats and rodents as reservoirs of zoonotic viruses: are bats special? Proc Biol Sci. (2013) 280:20122753.