Why would somebody donate 50 BTC? That is worth nearly 400,000$! 
Because, a couple years ago, 50 BTC was worth much less than it is now.
Although it wasn't cheap, the donation of 50 BTC was worth about $500 back then, according to https://99bitcoins.com/price-chart-history/ saying that Bitcoin's price was around $10 when the Donation system was introduced to Bitcointalk.
Next time, please think before asking.
Regards,
Trump