"...but I can't get to feeling that mere chance caused the multiplicity of existing things on this earth."

And that's not really what is claimed by those scientists who are not religious. They show how, once anything at all existed (in the 'beginning'), all combinations of atoms followed strict, but complex, laws of physics. To them...and to me... it is even harder to imagine some form of 'ultimate intelligence' setting out to design everything.

Once certain elements existed, it was inevitable that some would combine in ways that produced stars, planets, water, plants...and yes, even banjo players. ☺

Now...since we can barely imagine when & how that first 'creation' happened..(the "Big Bang" of science).. it is simply a matter of personal feeling whether to say about the original moment..."God did it" or "I have no idea"...or something else even stranger.

To those who 'feel' oriented toward a scientific explanation, saying "God did it" just pushes the question back one step to "why was there a god?" To those science folks, adding 'God' into the calculation makes the study over-complicated, since we don't have any standard measures or math symbols to represent such a concept. We KNOW we have atoms and forces and such which we have mostly learned to measure and count, but no one can agree on how a 'god' might be factored in.
   Of course, this doesn't deal with the emotional/moral/psychological/aesthetic/social/practical...etc.. values of having a vision of a "supreme Being" to turn to in times of crisis and for comfort and solice. Once humans could even imagine the idea of a 'God'...(50,000 years ago? 1,000,000 years ago?), it helped them deal with all the scary aspects of life...and death.... and I'd frankly NOT like to see all the leaders of churches and countries suddenly declare "We hereby renounce religion and assert NO belief in a god". Whether there is, or is not one, the idea is too deeply embedded in humanity to just suddenly discard.
*IF* humans decide to move away from religion, (and I doubt that this will ever really happen), it would have to be very slowly and because they really developed in such a way as to no longer 'need' religion to sustain themselves as they cope with confusion and problems.
All we can hope for is that those who DO choose religion and those who do not can learn to either discuss the issue quietly, or ignore each other....and I kinda doubt the 'ignoring' part will happen.