As of my knowledge update in October 2021, the top 10 countries experiencing rapid growth in eSports betting are:
1. China: With its huge population and a thriving eSports scene, China is at the forefront of eSports betting growth.
2. United States: The US has witnessed substantial growth in eSports betting, particularly due to the rising popularity of events like the League of Legends Championship Series (LCS) and the Overwatch League (OWL).
3. South Korea: Known as the birthplace of eSports, South Korea has a significant eSports following, and betting on eSports has been steadily growing in popularity.
4. United Kingdom: The UK has a well-established gambling industry, and its adoption of eSports betting has been notable, with numerous bookmakers offering eSports markets.
5. Germany: Germany has a large eSports community and a strong presence in eSports betting, making it one of the fastest-growing markets in Europe.
6. Sweden: The Swedish eSports community is vibrant, and the country has seen an increased interest in eSports betting.
7. Brazil: Brazil has a passionate eSports community, and betting on eSports has gained significant traction, especially with the popularity of games like League of Legends and Counter-Strike: Global Offensive.
8. Russia: Russia has a sizeable eSports fanbase, and the country’s betting market has been rapidly expanding to cater to eSports enthusiasts.
9. Australia: Australia has seen a surge in eSports betting, with many bookmakers offering markets on various eSports tournaments and leagues.
10. Canada: With the growth of eSports in North America, Canada has been experiencing an upward trend in eSports betting, mirroring the rise of the industry in the region.
Please note that the rapid growth in eSports betting can vary over time and may depend on legal regulations, infrastructure, and the popularity of eSports in different regions.