It's due to the World Cup
Most of the British barely knew of Qatar until the start of the World Cup. Thousands of British football fans have been there and were communicating back home via the Internet. Lots of journalists were there and filing reports on things other than the football. Now, lots of the British know a bit about Qatar.
The treatment of migrant workers in Qatar, including a large number of deaths, the country's stance on LGBT issues, and the treatment of women have not impressed the British. The UK treats asylum seekers badly, but most people see that through rose-tinted lenses, and prefer to think of themselves as compassionate people.
The sudden reversal on alcohol sales within the football stadiums shortly before the start of the tournament did not help. It seemed utterly unreasonable to the average British football fan, who wants cold beer in hot weather and feels it was promised.
The ability of the FIFA leadership to shape the views of visiting football fans is negligible. They're seen as interested only in money and power, and likely bribed by the Qatar government to award the tournament to a country with limited football culture.
The Qatar World Cup CEO, Nasser Al Khater, in response to the death of a migrant worker during the tournament, said "Death is a natural part of life, whether it's at work, whether it's in your sleep. Of course, a worker died, our condolences go to his family." That was really insensitive and meant that journalists stopped being interested in the Qatari view.
There's also drama in the European Parliament about alleged Qatari bribery. That probably isn't having much effect in the UK, but it won't help.
Overall, the whole tournament has come over as a very clumsy and expensive attempt at sportswashing.