51% is an 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 transactions rather has control over 51% of the staked amount. Both PoW and PoS are widely covered in detail by the online community so I will just drop a link so can know the basic differences.
PoW vs PoS
Not all 200k validators participate invalidation process in proof of stakeout of the whole pool of validators a few are chosen randomly to validate a transaction. In the case of Ethereum, it's called a validator committee which has 128 validators that verify the transaction. And the probability of having more bad actors in the validators committee rather than good is really low one in trillion here is the math for it
Please note the No of blocks added to the chain after the block containing your transaction. So if your tx is in block no 10 and the current chain height is 25 then the size of the confirmation will be 15. Confirmation ensures that there is no probability of fork before you use the funds. With each block confirmation, the probability of fork decreases exponentially. Confirmations do not mean the number of validators that confirmed your blocks