I'd consider getting fired a much more serious form of ostracism than deplatforming. Getting banned from Twitter doesn't affect your ability to pay rent.

I personally put the blame for his firing more on the blatantly distorted and sometimes even outright counterfactual coverage of his message. The number of mainstream and well respected outlets that falsely claimed he wrote that women are biologically less capable engineers, rather than that they lower predilection to enter the field , was disturbing. After his memo Google announced that they wouldn't set quotas for groups beyond the demographic's representation in the field. The people I know at Google felt that the reaction was overblown.