So I'm very interested in Speedrunning Marathons and I have a few questions

First, How do marathons stream other people's gameplay, like how does GDQ Stream the runners gameplay if they aren't really there and everything is done online?

Second, How would I go about Promoting a Marathon, How would I get it popular enough for many people to donate and most importantly participate in it

Those are the only question I have ATM about Marathons

Thank you for your time and I'm looking forward to your replies