Just as Riemann did not discover a 4th dimension, he postulated it, Einstein did not discover a space-time continuum, he postulated it; Einstein having postulated a space-time continuum did not cause it to come into existence. Before Einstein, Riemann (whose geometry is the foundation for Einstein's space-time continuum postulation) postulated the geometry of four and more dimensional curved spaces. Riemann's postulations and the math he developed based on his postulations, did not cause a fourth dimension (or higher dimensions) to come into existence. The point is that Riemann’s and Einstein’s postulations (ie. their imagined creations) are neither correct nor incorrect, they are unverifiable speculations which could be correct or incorrect.
Euclidean geometry is verifiable in our universe. The Earth is not flat, the Earth does not go around the Sun in a rectangular orbit, but Euclidean geometry applies perfectly to the Earth and its orbit because every point on and inside of the Earth and between the Earth and the Sun can be described perfectly using only three coordinates, each of which is at a right angle to each of the other of the coordinates. Those coordinates are usually called the X axis, Y axis and Z axis.
You have all seen the drawings of the sheet of rubber with the ball placed on it, and the curve which the ball makes in the sheet of rubber, and you have been told that the sheet of rubber is the space-time continuum of General Relativity and that the curve in the rubber is what we call gravity. If there was a space-time continuum and there was only one object in the entire universe, that ball on the sheet of rubber diagram would be reasonably accurate. But the reality is that there are at least trillions of balls (stars, planets, moons, comets, asteroids), and the sheet of rubber is (according to Einstein) a sphere or an ellipse, therefore, it is not just a surface area but it also has an interior, with trillions of interior curved deformations many of which overlap. My imagination isn't sufficient to do the following, but if you can, Imagine a golf ball that is 1,000 meters in diameter, with 1,000,000 irregular shaped and regular shaped different sized dimples along its entire surface and in all of its insides, some of which overlap and some of which do not overlap, that would be a very simplified example of the space-time continuum universe as envisioned by Einstein. It is mathematically provable that such a universe could not exist, but that is an effort I would not go to for free.
As I am not willing to provide such a time consuming mathematical proof here, if what I have written above has not already convinced you that Einstein’s geometry for the universe is very unlikely to be correct, consider the following:
In Einstein's Book, at page 104, to calculate the mass of a distant dwarf star Einstein used Euclidean geometry and Newton's gravity equations, which are for a Euclidean Universe; Einstein did NOT use his equations or a non-Euclidean Universe model.