It’s changed over time, but lots of time blocking and making sure systems were in place to have them keep running when I moved to something else. In the early days my time was focused by splitting days, then sets of days, then weeks, sometimes even months.
When I leave one, I am making a decision that this pillar stops when I leave or it’s continued by other’s. SEO for example, once I had it down I was teaching my team to run it and putting in check points for them. (weekly meeting with a standardized report/format) this way I could keep up to date and steer as necessary, but was out of the “day to day” unless something big came up.
Once I built up reliable people as ICs or managers in place, weekly check-ins with them keep the pillars going. These check-ins may change over-time from daily, weekly, to monthly, to quarterly… but that’s how they don’t suffer.