Upon reflection was it really a massive surprise

[Rosieredapples]

I've name changed for this as I'm likely to get flamed but I wanted a broader scope than my friends.
AIBU to say upon reflection the end of a relationship isn't usually a big surprise, regardless if its cheating, breaking up due to work demands, not getting on etc.
In my group of friends a very close friend was cheated on multiple times by her husband....he's a complete knob but I didn't believe her when she says it was a complete surprise, she had confided in our friendship group that their relationship had been rocky, that he had been unfaithful before. Now a year on she tells us many awful things and how unhappy she had been so I feel like upon reflection it's not a surprise at all but she won't acknowledge it.
I was married very young at 22 to my boyfriend from Uni, we lasted 18 months, it was not a surprise we didn't last and upon reflection twenty odd years ago I can see it was a disaster from the start.
Another friend took a job in a different city (a four hour journey away) and expected her relationship would not feel the strain. It did and they broke up. I know countless women who say their husband being unfaithful was a complete surprise but later admitted the relationship had been in trouble / coasting / unhappy. Genuinely I don't know anyone who could 100% say everything was perfect and a split was a huge surprise.
If you can barely speak to each other or are turning to other people outside your marriage how can it be a surprise it didn't work???

Sometimes things we know come as a surprise. I don’t know why! Perhaps we just don’t admit things even to ourselves.

Like admitting to not trying very hard at work and yet wondering why a colleague who is hardworking got promoted above you, fairly obvious why etc.

Breaking up with my ex was a complete surprise. We were working towards moving in together, had never argued, etc... but he turned around one day and just announced that he was breaking up with me. Genuine surprise, no red flags that it was going to happen. Looking back it was a good thing, I didn't see how toxic he was as a person, but I hadn't noticed anything until a few months after when friends and family started talking about the things they'd noticed that I hadn't. It can genuinely be a surprise sometimes because people can be unpredictable.

Yes perhaps it's the unpredictable or unusual out of character behavior that's the surprise not the actual breaking up. I was not surprised my marriage broke down but I was surprised at his attitude to the practical splitting side of things and he turned from someone I knew and loved to someone I couldn't hold a basic conversation with.

I was utterly blindsided by my husband leaving me, complete and utter shock and disbelief. The hurt still resonates 6 1/2 years later. We had a toddler, a baby he'd begged for and I had late in life for him. I will never get past that. A lot of therapy, however, has made me realise what an utterly shite husband he was and I just put up with it. You live and learn.

I think there are situations where something comes as a massive shock, but people only see the warning signs with hindsight.