How did you determine;
a, that the universe is as it is because no other way is possible?
b, that the universe is infinite?
c, that an internal or external agent is irrational?
d, that "universal connected reality" is all there can be?
Before you answer might I point out that I am referring to actual existence rather than notions of the mind.
a. Causality and non-causality are mutually exclusive states. The assumption that causality is behind all actions is not a logical fallacy. Unlike black swan events where it is a fallacy to induce that because all observed swans are white, all swans are white, where one state excludes the other we may exclude by observables. For example, if god were to be proven, atheism would be disproven. Likewise, if we observe causality, non-causality is disproven. There is a further similarity. Proving god does not exist is not possible. Similarly, proving non-causality is also impossible (possibility of hidden variables). Therefore, the burden of proof falls to the other side. Unluckily for the theists, they've never provided any proof of god. Luckily for determinists, the evidence for causality is all around. Before you state that quantum fluctuations / radioactive decay etc. are probabilistic / undetermined events, I cite this link
http://xxx.lanl.gov/pdf/1111.3328v1.pdf This logically reasons that quantum events are as physically determined as a coin toss - the outcome the result of real physical events. Probabilistic interpretation therefore is just a necessity of complexity and tractability. This could have been reasoned from the consideration that non-causality is not a state compatible with causality. They are either / or conditions. Therefore, determining that each event (its wrong to separate events but we must do so for mental manageability) is the logical progression in a highly complex chain, the universe cannot be any other way than it is.
b. I'm not saying the universe is infinite. It must be both finite and infinite. Therefore a fixed universe but one that appears from within to change. A zoetrope of space-time creation and destruction, the same moment, from a subjective point of view, recreated over and over. Sort of a standing universal wave function. In this way we avoid singularities and imaginary timelines. Also creation myths.
c. All thing being a continuum (there can be only one expressed nothing / everything - even my maths tells me this), then there can be no 'external'. Similarly, there is no self-contained internal. You cannot border off sections of the universe such that they are not connected. This means there can be no self-contained agency. Everything that occurs is part of universal expression.
d. By what mechanism could there be anything else? 2x0=0. You need 0 (nothing) to get 1 or - 1 (something/everything). Since there is only one unit of 0 (nothing), there can only be one expressed something (everything).
It goes without saying I reject multi-world hypothesis. You need only look at the ocean to sea why. Quantum fluctuations make sense if considered as the observable interference patterns of waves. Waves which, at our Planck length level of reality, we are unable to detect / observe. We must deduce them from observable actions. Shadows on the cave wall.
Of course, my model is abstraction. Impossible to prove or check. We have no external means of calibrating.