Why can’t tenants redevelop if landlord is absent?

The landlord of our building has been absent for the last 15 years, neglecting both rent collection and maintenance. During the COVID-19 pandemic, his descendant reappeared and is now demanding rent in cash, claiming the building lacks a bank account. The building has significantly deteriorated. Tenants are hesitant to fund repairs, especially since a builder has proposed redeveloping the property. Most tenants have given consent for redevelopment, and the builder has already acquired adjacent properties. However, the landlord is unwilling to agree to redevelopment, despite fair compensation offers.