I should also check if there are any notable events in 2021 that affected the site. For example, was it taken down or moved to different domains? How responsive were authorities? Maybe mention any law enforcement actions or international efforts like Operation in some region.
Need to structure all these points coherently. Maybe start with an overview, then context (2021 and pandemic), how the site operated, legal and ethical issues, impact on the industry, user demographics, security concerns, and finally conclusions about its significance in that period.
Also, think about the technical infrastructure. How did they bypass copyright? Maybe using cloud services or torrents. Were they hosting the files themselves or linking to other sources? Security measures for hosting pirated content might be discussed here.
Make sure to highlight the significance of the site in the context of 2021. For instance, during the pandemic when streaming services were overwhelmed or less accessible, people might have turned to piracy more. Or maybe new types of movies released in 2021 were particularly pirated.
I should also consider the language and audience. The blog post should be informative but accessible, avoiding overly technical terms unless explained. Use statistics if possible, like the number of users, downloads, or revenue loss estimates attributed to sites like 300mbmovies4u.
Also, consider the role of social media in promoting the site. Maybe in 2021, there were campaigns or influencers mentioning it, increasing its reach.
Make sure to include specific data points from 2021 if available. For example, "A report by XYZ in 2021 showed that 300mbmovies4u contributed to X% of all movie piracy in region Y."