Their assets in Switzerland would be priced in CHF. It could be a good diversification from USD-priced assets they have at home. There was a single-day 30% pop in CHF a few years back.
The recent decline of sterling is great for foreigners interesten in acquiring London property -- London will always be London, brexit or no brexit. But it just got a lot more interesting for foreigners with businesses (or investments) abroad to relocate there.