The wiring diagram is not correct (although it works)

[Pommfriz]

The output port of the MPPT is 5V, but the ESP is a3.3V-controller and regarding to the datasheet the ports are not 5V tolerant.
So a levelshifter is needed if the ESP should work longer.

[larsfcfa]

According to OpenDTU even a Galvanic separation via ADUM1201 is recommanded

[DG2DBM]

As far as I know, some Victron gear have 5V and some 3.3V output on the serial port.

I think Victron put some resistors in the output lines as a protection from shortcurts. So together with the clamping diodes in an ESP it may work.

Victron itself uses galvanic isolation. The following circuit works well:

[softwarecrash]

the esp famaly cant output 5v but is tollerant to 5v