From Politico Newsletter:

There is frustration in Whitehall that Tory MPs did not grasp the arguments made to them by Johnson and Javid. Multiple figures from across the government privately blasted Tory backbenchers as out of touch with what is happening with Omicron. One Tory suggested that their MPs suffer from their own COVID “lag” — only realizing how serious things are well after everyone else. Another thought some MPs had backed themselves into a corner by publicly committing to opposing the measures before the extent of the Omicron danger became clear. 

There is also annoyance that MPs did not seem to accept that even if the vast majority of the population is vaccinated, and even if Omicron is milder, the sheer numbers mean that hospitalizations could still breach hospital capacity. Another minister said a rebellion on vaccine passports paled into insignificance when compared to the prospect of the NHS being overwhelmed: “To be honest arguments about masks and certification are out of date. The focus is on boosters and saving lives.”