I know that 51% is the minimum percentage for confirming nodes for consensus.
However, in ETH for example:
ETH 2.0 staking has breached 200,000 validators
But I was able to sell ETH when I get 15 nodes (or around that number) confirmation.
So number of validations to commit my transaction was way less than 51% of 200K.
Can someone please explain to me what I'm getting wrong.
51% is and attack vector for Proof of work (PoW) consensus mechanism. While Eth 2.0 uses Proof of stake (PoS) which is less prone to 51% attack and it does not require 51% nodes for confirming transaction rather having control over 51% of staked amount.
Both of PoW and PoS are widely covered in detail by online community so i will just drop link so can know the basic differences.
PoW vs PoS
Not all 200k validators participate in validation process in proof of stake out of whole pool of validators a few are chosen randomly to validate transaction. Incase of Ethereum its called a validator committee which has 128 validators that verify the transaction. And the probability of having more bad actors in validators committee rather then good is really low one in trillion here is the math for it
Confirmations No of blocks added to the chain after the block containing your transaction. So if your tx is in block no 10 and current chain height is 25 then confirmations size will be 15. Confirmation ensure that there is no (close to none) probability of fork before you use the funds. With each block confirmation the probability of fork decreases exponentially. Confirmations does not mean the number of validators that confirmed your blocks