Vue 3 Realoading component if variable change

<LeagueTopScorers /> does re-render when selectedLeague changes ¹, but it doesn't re-mount. It only mounts when selectedLeague changes from a falsy value to a truthy one (because that's when the value of the v-if changes).

There are a few problems with your question:

• you're asking about a technical aspect (let's call it X), which you think will solve a business requirement (let's call it Y). It's a classical XY problem. Why don't you describe the Y requirement? (e.g: what you want to achieve). What output change do you want to see on what input change?
• the code you posted is not enough to create a runnable example. We don't know what v-select is, what <LeagueTopScorers /> is, or how does :is prop look like on <LeagueTopScorers />.

From the snippet you posted, I am guessing the following:

• v-select is either vue-select or Vuetify select component
• you expect :is to work on <LeagueTopScorers /> as it does on <component />. Hint: it doesn't, unless you coded it yourself, which I doubt
• last, but not least, I guess you want some code you placed into an init lifecycle hook of <LeagueTopScorers /> (e.g: onMounted) to run when you replace an object stored in selectedLeague with another object.

If I'm correct, the simplest and cleanest way to achieve this behavior is to create a computed ²:

const leagueId = computed(() => selectedLeague?.id.toString() || '')

... and use it in v-if, :key and :selectedLeague:

<LeagueTopScorers
  v-if="leagueId"
  :selectedLeague="leagueId"
  :key="leagueId" />

(without the <div v-if> wrapper).

The above will create a new instance of <LeagueTopScorers /> every time leagueId changes and will only render one when leagueId is not falsy. I believe that's what you were trying to accomplish, technically ³.

Notes:
¹ - to verify, use onUpdated(() => console.log('updated...'))
² - use selectedLeague.value?.id.toString() if selectedLeague is a ref
³ - at the same time, I am sure the actual business requirement can be met without creating a new instance of <LeagueTopScorers /> every time leagueId changes, but I can't help more without more details and/or context