Hi Catherine,
There are a few ways you could think about this.
The first, and perhaps the most cynical, is an out-and-out agenda to bring Britain to its knees. With everything that's happened since 2016, one, at times, can't help but think they're doing it on purpose. (The people who orchestrated Brexit knew exactly what they were doing).
The second has to do with what the Conservative party is - or what it likes to think it is: the party of low taxes. Now, this mentality will rarely ever, if at all, be applied to those who actually need a tax break (to, you know, afford to live and that) but it will be applied to big corporations. Sunak could well have to face an internal revolt for taxing the energy companies, and risk being called "not a true Conservative." It also destroys the whole notion of it being "the party of aspiration."
The last thing that comes to mind is lobbying. British politicians always, regardless of which side of the isle they sit on, receive gifts from the corporate world. Now, as I already wrote, the energy companies themselves don't seem to be against a tax hike. But other big companies could indeed be worried it's going to set a precedent they won't like. Someone, somewhere, is "expressing this concern" to government.
As far as re-election goes, Labour's lead over the Tories went down post Sunak's selection. It was a case of it being too good to be true anyways. They're probably confident they can get back to winning ways by the time the next election rolls around + the British electoral system is way out of date. Johnson bagged an 80 seat majority with only 43.6% of the vote. So if I was a Conservative, I wouldn't be too worried.
Thanks for reading,
Sikander.