Because it is like a lottery. You're not bound to win all the time, even if you "bought" the majority of tickets.
Everyone basically has a % chance of finding a new block ( which correlates with the amount of hashpower you have ofcourse.)
Unless ofcourse you do a 51% attack, https://www.investopedia.com/terms/1/51-attack.asp, where certain blocks would be orphaned (not confirmed, since nodes are bound to follow the longest chain.
You could basically prevent other miners from mining any blocks, since you hypothetically will always find a block before they do ( and thus creating the longest chain.)