Passive earnings are easy to make but need consistent work, that's the only factor in my opinion that makes it difficult. In crypto you can mean passive earnings by joining airdrops, as once you will start to join airdrops, in 6 months, you will join more than 500 airdrops, and all of them won't be fake, let's say only 10% might be fake, and remaining ones, will make you passive earnings, and the overall average of the 6 months will be more than enough.
And it isn't finished here, that 6 months of work will be helpful after that too, because many projects ask us if we did that task 3 months ago or not, if yes then only we can join otherwise not, so if you have worked 6 months and joined all the airdrops, then you will be able for that too. That's why I said airdrops are passive way of earnigs. I can also name other passive earnings method like staking, but I don't practise them so I won't mention them.