~ then you can manipulate some part of the blocks.
nodes can reject on if the older blocks are changed or manipulated somehow.
In case it was not clear, in a 51% attack the attacker changes the "tip" of the chain not some random blocks deep into the chain. keep in mind that what we have in Bitcoin is a block-chain and if anything, even a single bit is changed in any old block, that block and the whole chain after that block become invalid.