Module: Mathlib.Condensed.Light.Sequence

Goal state before:
pp: S T : LightProfinite
π : T ⟶ S ⊗ ℕ∪{∞}
inst✝ : Epi π
this : CompactSpace ↑(S' ⇑(ConcreteCategory.hom π))
S'π : (n : ↑ℕ∪{∞}.toTop) →
  LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π)) ⟶ LightProfinite.fibre n (π ≫ snd S ℕ∪{∞}) :=
  fun n ↦ { hom := TopCat.ofHom { toFun := fun x ↦ ↑x n, continuous_toFun := ⋯ } }
y' : LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π)) ⟶ S :=
  ConcreteCategory.ofHom { toFun := y ⇑(ConcreteCategory.hom π), continuous_toFun := ⋯ }
π' : pullback π (y' ▷ ℕ∪{∞}) ⟶ LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π)) ⊗ ℕ∪{∞} := pullback.snd π (y' ▷ ℕ∪{∞})
σ' : ↑ℕ∪{∞}.toTop → ↑(LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))).toTop → ↑(pullback π (y' ▷ ℕ∪{∞})).toTop :=
  fun n ↦
    ⇑(ConcreteCategory.hom
        (pullback.lift π (y' ▷ ℕ∪{∞}) (S'π n ≫ LightProfinite.fibreIncl n (π ≫ snd S ℕ∪{∞}))
          (lift (𝟙 (LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))))
            (CompHausLike.const (LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))) n))
          ⋯))
hσ :
  ∀ (x : ↑ℕ∪{∞}.toTop) (s : ↑(LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))).toTop),
    ((ConcreteCategory.hom π') (σ' x s)).1 = s
hσ' :
  ∀ (x : ↑ℕ∪{∞}.toTop) (s : ↑(LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))).toTop),
    ((ConcreteCategory.hom π') (σ' x s)).2 = x
⊢ ∃ S' T' y' π' g',
    Epi π' ∧
      Epi y' ∧
        π' ≫ y' ▷ ℕ∪{∞} = g' ≫ π ∧
          IsSplitEpi (LightProfinite.fibreIncl ∞ (π' ≫ snd S' ℕ∪{∞}) ≫ π' ≫ fst S' ℕ∪{∞}) ∧ Epi (cover π')

Tactic:
have : CompactSpace (fibres π' σ') := isCompact_iff_compactSpace.mp
    (fibres_closed π' (by fun_prop) σ' (by fun_prop) hσ').isCompact

Goal state after:
S T : LightProfinite
π : T ⟶ S ⊗ ℕ∪{∞}
inst✝ : Epi π
this✝ : CompactSpace ↑(S' ⇑(ConcreteCategory.hom π))
S'π : (n : ↑ℕ∪{∞}.toTop) →
  LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π)) ⟶ LightProfinite.fibre n (π ≫ snd S ℕ∪{∞}) :=
  fun n ↦ { hom := TopCat.ofHom { toFun := fun x ↦ ↑x n, continuous_toFun := ⋯ } }
y' : LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π)) ⟶ S :=
  ConcreteCategory.ofHom { toFun := y ⇑(ConcreteCategory.hom π), continuous_toFun := ⋯ }
π' : pullback π (y' ▷ ℕ∪{∞}) ⟶ LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π)) ⊗ ℕ∪{∞} := pullback.snd π (y' ▷ ℕ∪{∞})
σ' : ↑ℕ∪{∞}.toTop → ↑(LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))).toTop → ↑(pullback π (y' ▷ ℕ∪{∞})).toTop :=
  fun n ↦
    ⇑(ConcreteCategory.hom
        (pullback.lift π (y' ▷ ℕ∪{∞}) (S'π n ≫ LightProfinite.fibreIncl n (π ≫ snd S ℕ∪{∞}))
          (lift (𝟙 (LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))))
            (CompHausLike.const (LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))) n))
          ⋯))
hσ :
  ∀ (x : ↑ℕ∪{∞}.toTop) (s : ↑(LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))).toTop),
    ((ConcreteCategory.hom π') (σ' x s)).1 = s
hσ' :
  ∀ (x : ↑ℕ∪{∞}.toTop) (s : ↑(LightProfinite.of ↑(S' ⇑(ConcreteCategory.hom π))).toTop),
    ((ConcreteCategory.hom π') (σ' x s)).2 = x
this : CompactSpace ↑(fibres (⇑(ConcreteCategory.hom π')) σ')
⊢ ∃ S' T' y' π' g',
    Epi π' ∧
      Epi y' ∧
        π' ≫ y' ▷ ℕ∪{∞} = g' ≫ π ∧
          IsSplitEpi (LightProfinite.fibreIncl ∞ (π' ≫ snd S' ℕ∪{∞}) ≫ π' ≫ fst S' ℕ∪{∞}) ∧ Epi (cover π')