Development was extremely efficient back then. Delphi was even better than VB6, with RAD.
It's a bit sad there hasn't been any progress here in 25 years.
However web applications are a more complex use case overall compared to desktop applications.
I think they used a frameset with frames. It had the advantage that it could be sized to the browser window as a percentage and both frames could be refreshed/loaded independently without affecting the other.