Don't blame indie hacking for your failure. Just blame yourself.
You failed because
1. Your idea is shit
2. You didn't put enough energy in your work
3. You chose the wrong niche
4. Your marketing channel is not the good one
5. It's not the good time yet for your idea
6. PUT MORE EFFORTS IN MARKETING for god sake
7. Your product sucks
8. Your design sucks
9. You suck. Well, you don't actually suck, but what you did in this startup sucked. No big deal, you learn, it's part of any trip you'll take in your life. You don't become number one without trying and sucking.
10. You try to sell to people with no money
11. Nobody gives a damn shit about what you want to sell. Shit sweets? We are not in Hogwarts, eat them yourself.
12. You didn't pivot
13. You didn't listen to your users
14. You are too lazy
Any reason you chose here can be summarised in one: if you failed, it's your fault, not the rest of the world's.
Now, two options
1. Go do something else
2. GET UP AND KEEP FIGHTING