I appreciate this in an anecdotal but I've spoken to quite a few people I know in my family, that saw it as their civil duty to vote and they told all told me some variation of "there is nobody worth voting for", "I don't think it matters who I vote for".
I am sure many green voters felt the same way for many years and now they stand a decent chance of getting many seats!
I don't vote. There are many reasons I don't vote. However the biggest reason I don't vote is that the whole premise or at least how it is presented to you is false. The way it is presented to you both in school, media etc. is that you are supposed to read the manifesto, consider the candidates arguments and history etc. etc.
People don't do that, they vote for their team. People have their political teams, much like Premiership Football it often comes down to the "Reds vs the Blues" (literally Man U vs Man City).
The point clearly stands that had Reform not been a thing, 2024 would have been a conservative landslide.
What we got was a Labour landslide, what we should have got was some coalition.
It's certainly not a given that all the 2024 Reform vote would have gone to the Conservatives: a good chunk of it would have likely been disgusted abstention, another chunk to other anti-system parties (mostly of the right fringe, I suspect, but not excluding the Greens despite wild ideological differences), and likely a further (if smaller) chunk to other parties which were simply not the Conservatives (including Labour and the Lib Dems).
Edit: the best analysis on this is likely to be in the latest volume of the long-standing The British General Election of XXXX series, which has just been published online[0]. I haven't had time to look at it yet, though.
Also not every Reform voter would vote Conservative if Reform didn't exist.