I don’t find this very plausible. Let’s say in Cosmos, you have new blocks every few seconds. If one validator doesn’t include any new validators bonding, it just means they might get in a block later. Same thing with redelegations/unbondings/etc. It will also be very obvious what you are doing and cause a community backlash.
It only starts to work if you can prevent new validators from joining the set at all. But for that you need to form a cartel of at least 1/3 of the voting power. Then you can censor any blocks that add new validators (or include transactions where somebody removes stake from you.)
But we already knew that if >1/3 of stake is malicious the security assumptions break down. So that’s not really a new or surprising thing.