Who are the all time most important people in STEM?

Leibniz.

Cauchy
Lagrange
Laplace
Lavoisier
Galois
Poincare
Fermat

the messiah

Bill Nye the I only have a BS in Mechanical Engineering and no Masters or even took the PE exam Guy

true, you're using many of those just by being able to read the list (being on a computer)

Laplace was a fraud, he stole the Laplace Transform from Euler and slapped his name over it.

Euler spent a significant amount of time in the mid-18th century working on differential equations. One of his many noteworthy contributions in this field was the idea of transforming a function X(x)X(x) into a new function zz via the equation

z=∫e^ax X(x) * d(x)

which looks fairly similar to the modern Laplace transform, only with an indefinite rather than a definite integral. In a 1753 paper (entitled Methodus aequationes differentiales altiorum graduum integrandi ulterius promota), Euler used methods based on this transform to give a systematic method of solving second order linear differential equations. Later in his career, he further clarified the method and introduced the definite integral form.

In particular, this expression appeared in Euler’s 1768 Institutiones Calculi Integralis, vol. II

tl;dr - Fuck Laplace

How about Maxwell? Where is Maxwell? Why nobody remembers Maxwell?

In an age where people think it's no longer possible to be a renaissance man, von Neumann was just that.

von Neumann was hardly a renaissance man. A renaissance mathematician, maybe.

He did work in a few very tightly related fields (math/physics/the infancy of CS) and the only noteworthy thing he did outside of that was remember a ton of historical bullshit because of his meme memory.

I'm not even a mathematician or a physicist (I'm a chemist) and many of those are totally relevant to me.

Cummutation theorem
Coupling constants
Decoherence theory
Density matrix
Ergodic theory
Monte Carlo method
Operator theory
Spectral theory

There are probably a bunch of others that are important to me, but I don't even know it.

Not only did he make major contributions to almost every field of science, but he was a renaissance man, with extensive knowledge of history and other fields as well.

Von Neumann just goes to show that the Nobel is not the be all and end all of scientific achievement that brainlets make it out to be:

"When asked why the Hungary of his generation had produced so many geniuses, Wigner, who won the Nobel Prize in Physics in 1963, replied that von Neumann was the only genius."