He's not, not really. This is neither directed at the guy nor is it all that fanciful. To understand it you do need to read it very carefully, though, this is kind of an "intellectual exercise" bit from Mark in my view. Sorry, this will be a long comment.

So the rich man asks Jesus for how to inherit eternal life, and he says "you know what to do," and the man says "... but I've already been doing that." Jesus does not contradict him by pointing out any broken commandments. So if you read carefully, as far as that first part of the exchange goes down, Jesus has promised that this man merely has to keep firm with these commandments and he will inherit eternal life.

But, this man has already been doing what he's supposed to be doing, and somehow he's still here asking Jesus to help him out. The careful reading is that the rich man has a conflicted, uncertain heart. He has been promised eternal life but wants the certainty that Jesus is correct. And Jesus then "loves him" and offers him a way to get precisely that certainty, basically saying "leave everything behind and follow me... You want the proof that I am who I say I am and when I promise that you have eternal life, you can be sure of that promise? The only way is to live with me for a long time, see the masses healed, see the sacrifice that I am about to make for you on the cross, and then you will have this certainty."

The selling of stuff has two functions that the text calls out here, the first is to "give the proceeds to the poor and you will have treasure in heaven," notice that this does not speak directly about inheriting the kingdom, Jesus already covered that part. This is about getting even greater rewards and celebration once you get into the kingdom, because you took care of the poor and needy in this life and that will be part of your legacy. And the second is "then come, follow me." The problem in the last part is that the property is an obstacle to following Jesus, it is that this guy can't leave his property behind without neglecting it, or else he's going to have to leave Jesus later to make sure that the fields are being plowed and the sheep are grazing and whatever else his property is doing for him. Property implies responsibility, Jesus is asking him to lay down all his other responsibilities if he wants to become a follower and have the certainty that he wants to achieve.

So Jesus doesn't say to bugger off, he says precisely the opposite, to not bugger off... and then the guy buggers off anyway! It's a theme in Mark that usually when Jesus or an angel tells someone to do something, they do the exact opposite. "Go and proclaim the good news! ... and the women didn't tell anybody." This is one of those cases. "Stay with me, I'll give you the certainty you crave" and he just goes off upset.

At this point he "went away," he's not the recipient of the camel/eye-of-the-needle saying, which is addressed to Jesus's disciples, almost exasperatedly.

Jesus says of this situation, where the man goes away grieving because of his possessions, "How hard it will be for those who have wealth to enter the kingdom of God!" And the disciples are "perplexed," to which Jesus first broadens to "Children, how hard it is to enter the kingdom of God!" (some texts add "for those who trust in riches" but I think that was not original here). And then he targets the camel/eye-of-the-needle analogy specifically at the rich.

If you understand all of this context then the camel thing makes sense, he literally has to shed all of this extra body-weight -- the responsibility, the worry, the misinterpretations when even a hint of danger towards your carefully curated nest egg presents itself -- to get the flexibility and finesse needed to just do the right thing and follow where Jesus leads him. It's not directly about "sell all of your stuff and give it away or bugger off", the careful reading is that it's about "stop lugging all of this dead weight around, because you can't take it with you anyway when you die and your soul passes through that tiniest of gates. If you're attached to all this baggage you won't be able to make it."

This is probably related to several mystical interpretations of Jesus's own ministry on Earth being related to a process of "self-emptying" but this comment is already way way too long.