how do pro players not get taken by surpise

This isn't just a pro thing. It's a legitimate skill set. I'd say that for pros it's a must-have. For me, far from pro, it's something I can learn and practice that only requires my brain. Unlike mechanical skills which to me are just black magic or cheating and no amount of practice will improve.

It starts at a macro level by knowing whether the area you are in is clear or not, or how close enemies might be and how fast they could show up. And how likely they are to show up. All of which is knowable just by paying attention when dropping and not dropping into a congested area. Watch other players come down during drop. Knowing where they land and where the first circle will be... is pretty much all you need to know in order to reliably predict where people are, where they're going to go, and when they're going to be on the move. After a while you don't even need to watch drops. You'll get to know where the hot spots are on any given map, and those usually account for 70-80% of all squads in the match. Avoid them. Unless you're playing Wildcard.

It ends at the micro level by knowing where you can have visibility and cover and a quick exit. And verticality. And knowing if/how your squad can aid your mobility (Alter, Ash, Wraith, Valk, even Octane). Mobility is king in this game. In any shooter. I'm still awe struck every time a squadmate chooses Lifeline or Gibby. I always think, "There goes the match." Find a place from where you can strike, but also from where you can escape if needed. For me that usually means places up high. Because I don't know how pros do it, but I don't ever allow myself to be married to a position - a spot I'll hold or die. I hold a good positions if I can, but if it starts to look dicey then you have to have a way out, preferably a fast way out.

In the end what it mostly means is not randomly wandering around the map looking for action. There should never be anything random in your behavior. You should be moving for a reason (better position mostly) and knowing how to get there without having to engage until you're ready. If at all. Which means you need to know where other people are. As a Valk I'm using every survey beacon I can safely get to, and not just for the evo, often using one to see if the next one is safe. For me the knowledge is a tool of avoidance, but a more aggressive player could use it in just the opposite way. Whichever way you use it, knowledge is power.

(But also: there's a lot of cheating that goes on in this game. I've seen streamers/pros who are constantly looking away from their monitor... to look at some other screen that shows them where all their enemies are. Assume there's some of this going on most of the time, and the higher you go in the ranks I bet the more of there is. Nothing could make it harder to sneak up on them than them having wall hacks and live enemy positions at all times. People are scum.)

I see. Thanks for your response.

Games rigged brah, eomm, DMG, hit boxes, footstep audio and whatever else changes mid game/gunfight.. one game you'll hear all audio and hit every shot then next game you'll hear nothing and hit boxes and recoil are changed

EOMM Google it