I don't think there is an author who has not been rejected by the big publishing companies. I'm talking now of the days when the only way to get published was to be taken on by a main stream publisher. Nearly all the famous names who are now familiar to readers and scholars alike, were once rejected by one publishing house or another.
Now anyone can publish a book. It's easy. You write your book. You submit it to Kindle Direct Publishing and hey presto! you are a published author. Quite often with typos and bad grammar included.
Writing your tome is the easy part. Getting people to buy it, and maybe leave a comment about it, is the hardest part of being an independent author.
So how do people pick their next book these days? In 'the old days' when books were printed, you would go to a shop and look along the shelves for something that sparked your interest. Readers might scan the best seller lists and go in search of what was trending at the time. They would wait patiently for the next book from their favourite author. They might pick something by someone local to their community. They might wait for the paperback version or trawl through the pallets of books on offer at cheap discount stores. But the truth is few authors sold their books in vast numbers.
So how do authors get noticed now? There are hundreds of websites that offer to promote and advertise your books. I'm on several but I have not noticed any great response to these. Maybe I don't try hard enough. I'm not a naturally pushy person and to be a success I guess this is a flaw. You name a site and I bet I'm on it somewhere.
There are sites that boast of having mailing lists of tens of thousands of people which you can join, for a fee.
Social media - get the word out, but no matter how much you tweet and get re-tweeted, if people don't catch that message there is no sale.
What authors have to remember is that their book is a mere drop in the ocean. ANY sale is a success when there are literally millions of books from which the reader can choose. Well done to the few who make it to the top without the backing of the big guys. You are doing well. You are a success - just don't quit the day job yet!