These people are just too good for me

Ok, first tourney of the day. Not to mention that 2 hands before got sucked out w two pairs 94 flop K94. All in on flop vs AA. River A. At least the guy though he was ahead.

But plays like this just blow my mind.

Starting hand on BB I had 3000. SB had 16K+. Blinds 125-250. Mid position limps. SB calls, I check

Flop 53K. All diamonds. All of us check. Turn Ks. Not the worst card for me. SB bets 500. Great time to double up. Of course, can't just call. I shove almost 3 K, mid position folds, sb INSTA calls.

Flips 86. Nothing. River diamond. Monster flush.

I can do any math, count any outs, or whatever else, but I can't really understand it.

Maybe it's just me. Can somebody send me the book these guys are reading?