I can agree with that, but it has nothing to do with the question I asked you, or the claim that you made. That's just a guess at a base rate.

We only heard about Watergate because it was an investigation which happened to uncover a legitimate conspiracy. What about all the investigations into potential conspiracies which turned out to be nothing?

You said "if a conspiracy can be adequately hidden and achieve its aims, then it is very likely to be real". "If A, then B". You can prove that using "not B, then not A". That is, you can make up examples of conspiracies that weren't and see if you can also make up ways in which they could be hidden. If you can, your claim is false, if you can't, then your claim might be true (or you may not be sufficiently devious (or motivated)). But what you definitely can't use is "If B, then A" (Watergate was real and it would have been hidden without journalistic interest) to prove anything. Logic 101.

We only heard about Watergate because it was an investigation which happened to uncover a legitimate conspiracy. What about all the investigations into potential conspiracies which turned out to be nothing?

You said "if a conspiracy can be adequately hidden and achieve its aims, then it is very likely to be real". "If A, then B". You can prove that using "not B, then not A". That is, you can make up examples of conspiracies that weren't and see if you can also make up ways in which they could be hidden. If you can, your claim is false, if you can't, then your claim might be true (or you may not be sufficiently devious (or motivated)). But what you definitely can't use is "If B, then A" (Watergate was real and it would have been hidden without journalistic interest) to prove anything. Logic 101.

if a conspiracy can be adequately hidden and achieve its aims, then it is very likely to be real

This fact will be known to those contemplating such a conspiracy.

Therefore they are more likely to attempt it.

David