Sure but the difference with mining is that having a majority of hashrate doesn't allow you to maintain that majority in perpetuity. You have constant operating expenses that require you to sell your Bitcoin, along with constantly growing competition. Just look at the rise and fall of large Bitcoin miners. With PoS if you are the biggest on day 1 you will probably be the biggest on day 1,000.
It might mathematically keep you in charge forever, but if you can stop almost anyone from being able to profit then it's very unlikely people will invest enough to override you.
And the motivation not to do it is the same, people will get mad and stop using the grossly manipulated coin.
