You seem to be describing an extreme version of hard causal determinism:
- Everything has a cause.
- Each cause has only one possible effect.
- Therefore the only things that have occurred are those that are possible, and anything that hasn't occurred didn't because it wasn't possible in the first place. There is only one possible causal chain back to the origin of the universe.
Laplace most famously formulated this idea in what later become know as Laplace's demon: If a super being knew everything there was to know about the universe in terms of velocities, masses and positions of each an every particle, then that being would be able to calculate all of the past events that have ever occurred and know all of the future, since there was only one possible past and one possible future per the laws of physics.
Note that this position isn't compatible with current results from quantum mechanics (whether Copenhagen or MWI, or any other non-hidden variable theory).
After comments from the OP, adding a second possibility (pun intended)
The idea that everything that is possible exists (at some point or the other), could be a reference to Nietzsche's Eternal Recurrence.
Eternal Recurrence is a fairly intuitive concept once you accept the basic premise (popular in the 19th century) that time is infinite, but space is finite. Finite space implies a finite set of possible configurations of the material world. If time is infinite, then the universe will go through every possible configuration it can have, and eventually return to a configuration it has already been through before.