What killed delphi were its proprietary closed roots. With a single vendor with erratic market history behind it, it was risky to use it for anything that was needed to be updated frequently and last long.
Partly. But let's not forget Microsoft actively kicked Borland in the guts by withholding API information, and hiring away Borland's key figures. Everybody saw it and accounting for Msft weight (especially at that time) it was safer to bet on Borland's demise. I think it played bigger role then any erratic behavior.
Betting on a single OS which they didn't control, soon abandoning kylix, would not help either. Combine this with license prices and delphi lasting so much is both a miracle and testament to their quality. But definitely not something recommend today.