Look at the following pie chart from Blockchain.info . In the Unknown pie slice are private datacenters and ASIC manufacturers that are large enough to keep the 1% typical pool fee for themselves. Suppose there are four very large datacenters in there. Count the named pie slices and add say 4 for the private datacenters in Unknown and get 12.
Those 12 miners control Proof-of-Work Bitcoin mining.
Wrong, these "named slices" are not miners, they are public pools with thousands miners contributing to each one. The second those miners sense their pools get bribed to destroy bitcoin, their source of income, they would switch to non-corrupted one. Instantly, within a day. With each month passing and more and more money being poured in mining hardware the chances that hardware being obsoleted by some external bribing attempt are diminishing rapidly.