Mmmh. I suppose it depends on how you define 'a lot'. According to a poll by Lord Ashcroft (who, incidentally, was a Brexit supporter) the split among SNP voters was 64% to 36% in favour of Remain. The split among Conservative voters was 58% to 42% in favour of Leave. So the proportion of SNP voters who voted for Leave was lower (according to Ashcroft's poll) than the proportion of Conservative voters who voted for Remain.
https://lordashcroftpolls.com/2019/0...rendum-and-why
So, if everything is to be viewed through the prism of Brexit, then perhaps the Conservative party have more to fear from a loss of Remain voters than the SNP have to fear from a loss of Leave voters. Or, especially given that the UK has actually already left the EU (despite what some people seem to think), perhaps viewing everything through the prism of the historical Brexit vote is not particularly illuminative or informative. My own view, for what it's worth, tends to the latter. So what will drive the way people vote in future elections if not the way they voted in the EU referendum years previously? Events, dear boy, events. (As Harold Macmillan may, or may not, have said.) And my guess is that there are going to be a lot of them over the next 2 or 3 years.
May I ask where you got your information from to support your statements I quoted above?