Forgot to add Qubic was definitely intentional reorgs though. They did it for brief periods with significantly less than 51% of hash power. Same selfish mining attacks can be done with just about any PoW coin. It's an economic attack. Miners are incentivized to switch because they will get the the reward from the native coin + the attacking coin reward. It will always be worth more to do that than mining natively. There are several ways to greatly mitigate this though. Like variations of workshare schemes for example which is what Monero is in the process of implementing.