The past few years have seen a shift in security strategies from looking outward for external threats to detecting and defending against adversaries that have already breached the network. Dividing up environments effectively shrinks the attack surface available to adversaries. The more difficult it is for the threat actor to move around, the longer they will need to dwell in the network before reaching their goal, ultimately increasing the likelihood that they will be detected. Micro-segmentation plays a central role in the realization of zero trust strategies by severely limiting lateral movement of an attacker.
Source: https://www.helpnetsecurity.com/2021/04/22/implementing-micro-segmentation/