It is possible to build a new chain from the genesis to 300,000 in just 5 minutes with a terahash computer. When new nodes join the network, it is not possible for them to distinguish the real chain from fake chains. terahash computers only cost $3000

Minimum difficulty to mine blocks is 00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff or so.
When building your own chain, you can carefully select the time to write on the block so that difficulty stays at a minimum.

If someone created thousands of chains like this, would bitcoin survive?