There are five or six possible causes for mandela effects. It could be converging timelines, it could even be artificial intelligence reverse-engineering itself retroactively, using quantum computers, bose-einstein condensate and/or time travel to adjust the past in its advantage. Three ways to change the past:

1. Quantum computers
2. Bose-Einstein condensate. Check out its properties. This is how it's made:
3. Time travel
   Other possibilities:
4. A secret mass memory manipulation experiment.
5. Convergence of the timelines.

I'm not so sure if mandela effects prove we're living in a simulation. However, the chance we are not living in a simulation is immeasurably small.