This is the right one or you can put it like this.. It is a well known fact that professional athletes earn a lot of money.
Yes... this is the right one.
Let's take the second one;
"Professionalathletes is widely accepted that earn a lot of money"
... this has an obvious grammar issues;
athletes are / athlete is
"accepted" is not so appropriate word to use for this idea. "known" is a better word;
Professional athletes are widely known for earning lots of money