I think you’re leaving details out of your story. If the landlord wants to make a few bucks, then they keep their good tenants (lowers vacancy rate, keeps repairs low, etc).
Kicking out good tenants cost landlords money.
It’s pretty simple. There’s a tech boom or similar, a bunch of rich workers move in, rents go up. Landlord spikes rent by 30% to take advantage. You can see this happening in r/sanfrancisco today, for non-rent-controlled units.
And yet many landlords kick out good tenants, and take the risk that a new tenant that's willing to pay 30% more turns out to be a bad one.
Not sure why you're surprised: this sort of thing has been widespread for years in cities (like SF) where demand outstrips supply.