Bootstrap Gate Drive
This is a question about the weird behavior of your model, right? The wire between the diode and the capacitor is totally isolated as long as the diode is in reverse bias.

I would suggest adding a large (100 M\$\Omega\$) resistor in parallel with the capacitor and a similar resistor in parallel with the diode. There is always some leakage current across a capacitor or a diode, so this actually makes the component model more realistic. I bet the 5.99 V will pull down to 0 V in your model.