The meeting occurred randomly / was never supposed to occur -- which is the correct meaning of happenstance?

Question

I was learning English words on Vocabulary.com and came across the following question:

If a person met his/her future spouse through happenstance, which of the following is true?

• the meeting occurred randomly
• the meeting was never supposed to occur

There were actually four options but the other two were 100% wrong.

From those I'm giving, I chose the second one and it turned out to be wrong. Why is the first option correct?

To me, they seem to mean the same, to be honest. OALD gives the following meanings:

randomly
1. without somebody deciding in advance what is going to happen and without any regular pattern

be supposed to do/be something
1. to be expected or required to do/be something according to a rule, a custom, an arrangement, etc.
2. to be generally believed or expected to be/do something

Again, I don't see any difference.

• the meeting occurred randomly — that is, there was nobody deciding in advance that it was going to happen.
• the meeting was never supposed to occur — that is, it was never expected to occur according to an arrangement (because there was no arrangement).

I'd like to know if there's something I'm missing, or if it's a mistake.

Answer 1

The meeting was never supposed to occur does not mean, as you think, “it was not expected that the meeting would occur”.

• In the first place, the negative here, never, in fact does not govern supposed, although it looks like it should govern supposed. This sentence involves ‘negative raising’, which ‘raises’ a negative out of a subordinate clause into its superordinate clause. So never actually governs only occur ; the meaning might logically (but not idiomatically) be expressed The meeting was supposed to never occur.

• In the second place, suppose in this context does not have the 'epistemic' (probabilistic) meaning “regard as likely” but the 'deontic' (obligational) meaning “regard as desirable or mandatory”, as in “We’re supposed to hand in our papers in class Monday”. To say that some event was “never supposed to happen” means that the event was not intended to happen, and usually that steps had been taken to insure that it would not happen.

So that paraphrase is right out. Randomly isn’t a lot better—in contemporary usage it’s rather too strongly associated with calculations of probability to characterize events whose likelihood no one would ever calculate before the fact—but it’s closer than never supposed to occur.

Answer 2

Happenstance is defined as a chance occurrence. The key to the OALD definition is without any regular pattern. Something happenstance occurs without a pattern, or randomly.

There's nothing that states that the meeting was never supposed to happen; that would indicate that the meeting was not thought to be possible and/or a bad thing.

Answer 3

the meeting occurred randomly

matches the definition "randomly", so this answer is OK.

However, "supposed to" (having an expectation) is different from "never supposed to" (no expectation). So that explanation cannot be supported with the definition.