The SIM7000E LTE module can operate from 3.0V to 4.3V and in GSM transmit mode will demand 2A in bursts (577us every 4.615ms).
As the LTE module draws more current than the SYS regulation voltage can handle, this SYS voltage will drop to V_bat - 0.068V. Including the voltage drop across the diode, V_SYS will still be above the minimum supply voltage of the LTE.
As the MAX8934D has a 3.3V linear regulator and Li+ charging circuitry, it is well suited to a portable system which has a SIM700E LTE Module.