For example, if Bryan Singer announces a bunch of different film and television projects roughly at the same time....
1. Six Billion Dollar Man
2. Battlestar Galactica
3. The Munsters
4. Logan's Run
6. X-Men: First Class
....He will rummage through the above list and pick the easiest project to do (The Munsters), and jettison everything else.
Additionally, he has proven that he cannot do all of the above projects...at once.
Now, if he had a massive production company like the late and great Stephen J. Cannell did, he might have been able to delegate authority to make all of the above movies.