There are many reasons behind this because this is the law of our world where rich get more rich because they have money and they can invest in many things and can generate a lot of income from many sources and they get it increase and increase in money days by days and same case with Elon musk, Bill gates etc...
And other things that is poor has no money and no knowledge and also other such things and they have very less opportunities and thus there are very less chances that a poor man becomes rich and that ratio is very little considering that.
I do not agree with your statement, all the facts of life are not as you expected because the rich will not be eternally rich or vice versa that the poor will not be eternally poor in this world, throughout the journey of life until now that the wheel of life has always turned and some poor people have become rich because his hard work efforts have improved the economy for the better, life is very dynamic, so try to increase your finances until you are on the list of rich people, it will motivate other people to get the same opportunities.