MOSFETs acting strange on different power supply
I may be wrong, but IMHO 78XX needs capacitors to work correctly and as it is switching, it would generate noise until filtered out after. And the ESP also wants capacitors on power/gnd to have no noise and enought reserve in power for short peaks (especially when connecting/transmitting). Maybe your 3V3 source is stabilized enought for ESP to work somehow, but the 78XX so near produce so much noise, that ESP does not work (at all/reliably)