I can't tell why you were rejected, but I can offer you something to help bide the time: freelance work.
I was in a bit of a hole financially and getting a full time job would have killed my startup ambitions, so after failing to get any clients on sites like Upwork I applied to Toptal: https://www.toptal.com/#contract-just-respected-software-arc...
They screen their freelancers which means they've got fewer but higher quality workers. Your skills are similar to mine, so you should be fine to get in. Just don't give up, I failed the first time around but then I brushed up on my code solving abilities and got. Didn't take me a week to find my first client and I couldn't be happier with him or him with me.
I found an old HN discussion about Toptal after I got in, and realized it was mostly people screaming about not being able to get in, or considering themselves above solving code challenges. Just don't let that hold you back.
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That aside, I do have tips on your job hunt!
Right before I got into toptal, I began having conversations about employment through the HN hiring posts, but I had a better process than (I suspect) most.
1. I copied all the posts from Who's Hiring into a spreadsheet
2. through them all by hand and wrote a single paragraph about why I think I wanted to work for their company
3. I extracted email addresses into another field
4. I composed an email about how awesome I am
5. I combined all of these through a Mail Merge and sent out 10 emails a day, keeping track of them through Streak's pipelines.
I recommend this project. After this, I know I applied to exactly 53 companies (felt like millions) and received no replies from 27, and was rejected by 21 because of visa issues.
Streak's Career Search Pipelines are awesome. :)