Yes, we wondered that too
It's really unnerving when somebody shows an unhealthy level of interest in something you own and have made clear you don't want to sell. My only thought was why would he have bothered to come and ask to buy it in the first place if he was just thinking of trying to steal it? Also, we love it, but it's 23 years old and nothing special to look at, so why would you target that one over any of the much newer ones in the area (not saying that I want anybody to have their caravan stolen, mind)?
I'm not resting on my laurels, but he came across as cheeky and hoping to get himself a good deal rather than an outright thief, but how could we know for sure?
I think he was hoping that somebody maybe older or more vulnerable and less assertive would answer the door. Just a guess, but I've been overthinking this and, had I been more hesitant, his MO might have been something like this:
"It looks quite nice, but it's obviously very old, so not worth much - I'll do you a favour, though, and give you £200 for it."
"Don't be ridiculous - yes, it's old, but it's still worth at least £2,000!"
"Fraid not - i'm a dealer and I can tell you for a fact that a van of that age is worth nowhere near that - you'd be lucky to get £400 at the most for it, but I've got a customer looking for one of that make, so I'll be a fool to myself and give you £500 if we shake on it right now - I'll be lucky to make £50 profit on that myself, as a dealer."
"No, thanks, I told you we aren't selling it."
"But YOU mentioned the price you were hoping for and I just came back with a much more realistic - actually extremely generous - offer based on its true value. I'm very busy, you know - I hope you're not just trying to waste my time and play games with me, trying to rip me off."
As I said, way too much time overthinking it, but it just left me feeling rather unsettled. I can imagine an elderly or frail person could have been really scared indeed. We were genuinely pondering getting some of the old MN favourite penguin bollards for the drive some time - we're now strongly considering that as a matter of urgency. Probably a couple of cameras too. We were hoping to have a few days away at the seaside in half-term, but it doesn't look like that's going to be happening now with everything going on, so we might have a bit of money spare to spend on improved security.
This is what is so horrible about CFs who deliberately pressurise and try to harass you into giving them the knock-down deal that they believe they're entitled to - they may just be trying their luck, but they leave you worried about what their end-game might be, and often having to spend money on guessing and trying to thwart whatever lengths they may be willing to go to.