My DIY printer only boots when all my endstops are triggered. Why is that?
From your fault description of printer logic board losing power when endstops are released it sounds to me like those endstops are shorting VCC to GND when not pressed. That the fault also goes away when the endstops are unplugged reinforces this.

I guess the logic board has its own protected regulator because otherwise you would be shorting out the power supply and that would also turn itself off after likely causing a lot of damage to the logic board.