one anecdote i have heard is that many people's careers have benefited tremendously from the opportunity to act in their boss' role for a few months when their boss has fallen sick.

this clearly isn't a strategy you can actively pursue, but a potential opportunity to be aware of and react to.

it's also somewhat entertaining to reflect that many people who have ascended some rungs up the org chart may have partly done so because their boss happened to get sick once.