The French had no choice but to withdraw at Gembloux. The DLM's lacked the means to hold the ground with the tiny number of infantry troops available in them backed by very little artillery. Basically, the infantry component of a DLM was arranged much as later US mechanized cavalry was. That is, they had limited numbers of fairly well armed infantry and were intended primarily to supplement the armored units in reconnnissance missions and for use in screening (such as setting up a picket line) but lacked the depth and numbers to hold ground in the face of serious opposition.
The French tanks could not hold the ground on their own. They had little infantry or artillery support. The Germans were rapidly reinforcing with regular infantry divisions that were well supported.
Given the situation, what other choice did they have?