Earlier quoted context omitted.
I think the reason they preferred the vacancies is that the value of the property is related to the rent price, so if they lowered the rent they’d have to lower the book value of the asset as well.
I've heard that theory but it still doesn't quite make sense to me. Investors know that book values are usually stale. They're rarely used as a primary justification for valuation except in industries where mark-to-market is common like financial institutions. Real estate investors tend to focus on Net Operating Income, which a vacant property won't generate, and Net Asset Values, which are based on market values. So…
At a high level commercial real estate valuation cares about the cash flows for the entire building (usually over 10 years) and a discount rate to get to a number on what the building is worth. When we see empty space, we think it's not making money, but all landlords assume that a space will be empty at some point and for some amount of time, so that's already baked into those cashflows.
Without getting into the specifics, you'll generally push out your assumptions on leasing that empty space rather than drop your price on cost of the space. Pushing out assumptions typically means taking a slight hit because the cashflows you were already expecting are just hitting the books a little later. Dropping the cost of the space generally decreases market value, so that makes all of the space in your building cheaper which has a much more significant impact on the cash flow for the entire building, rather than just one space.
The other significant factor is that landlords typically have significant upfront costs in base building improvements and free rent credits that they give to tenants. This means that there's a certain amount of time, generally a few years, where the landlord has paid out more money to the tenant than they've received. Landlords need to be confident that the tenant is going to be paying rent beyond that break even point, or else they've lost money in addition to losing out the ability to rent it to another tenant and any legal fees associated with evicting a tenant.
Between how valuations are structured and needing to hit that breakeven point with a new tenant, there are relatively few incentives for landlords to just "lease the space".