The RAW makes sense to me, but okay, let's discuss 'surprise' outside of RAW.
You seem to have a knack for pulling the wrong meaning from text by taking it out of context. If you read my other reply you'd see that when I said "I won't argue RAW, because it's stupid." I didn't mean the rules are stupid, I meant arguing about RAW is a stupid pointless waste of time. It always devolves into pulling words out of context, torturing their meanings, or playing mind-reader with the author.
Lets look at a round from each of our viewpoints: A character doesn't notice a threat at the start of combat and is surprised by three Assassins' attacks. Initiative is rolled and Assassin #1 goes first, followed by Assassin #2, then the character and lastly by Assassin #3.
Here's the relevant section of the DMG:
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Any character or monster that doesn’t notice a threat is surprised at the start of the encounter.
If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends.
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Your view: The first Assassin's blade hits the character and auto-crits. According to you, the character is no longer surprised. The second Assassin hits but cannot auto-crit because the character is no longer surprised. The character's initiative comes up and he can take no actions because he used to be surprised. The third Assassin then attacks with the same conditions as the second.
My view: The first Assassin's blade hits the character and auto-crits. The second Assassin's blade hits the character and auto-crits. The character's initiative comes up and he can take no actions because he is still surprised. The third Assassin goes but cannot auto-crit because the character is no longer surprised.
I can see how you are pulling your meaning from the text, but it seems particularly forced to me. Whatever. I use my way because it makes sense to me. I don't see how you can no longer be surprised and yet still suffer effects of having been surprised in the past. It seems silly.
I can also easily imagine this scenario playing out:
A wizard is attacked by three assassins and is caught off guard by two quick attacks, but has the presence of mind to cast Shield (a reaction), deflecting the third assassin's blade.