-- Lean 4 proof step from Mathlib.Topology.Category.Profinite.Product (goal)
Goal:
ι : Type u
X : ι → Type
inst : (i : ι) → TopologicalSpace (X i)
C : Set ((i : ι) → X i)
J K : ι → Prop
inst_1 : ∀ (i : ι), T2Space (X i)
inst_2 : ∀ (i : ι), TotallyDisconnectedSpace (X i)
hC : IsCompact C
this : CompactSpace.{u} (↑C : Type u)
a :
  (fun (X : CompHausLike fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u)) ↦
      (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u))) : Type u))
    (limitCone (indexFunctor (X := X) (C := C) hC)).pt
⊢ ∃ (a_1 :
    (fun (X : CompHausLike fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u)) ↦
        (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u))) : Type u))
      (Cone.pt (F := indexFunctor (X := X) (C := C) hC) (indexCone (X := X) (C := C) hC))),
    (ConcreteCategory.hom (FC :=
            fun (x1 x2 : CompHausLike fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u)) ↦
            C((↑(x1.toTop (P := fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u))) : Type u),
              (↑(x2.toTop (P := fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u))) : Type u)))
            (CC := fun (X : CompHausLike fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u)) ↦
            (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u))) : Type u)) (X :=
            Cone.pt (F := indexFunctor (X := X) (C := C) hC) (indexCone (X := X) (C := C) hC))
            ((limitConeIsLimit (indexFunctor (X := X) (C := C) hC)).lift (indexCone (X := X) (C := C) hC)) :
          (a :
              (fun (X : CompHausLike fun (X : TopCat) ↦ TotallyDisconnectedSpace (↑X : Type u)) ↦ (↑X.toTop : Type u))
                (indexCone hC).pt) →
            (fun (X : CompHausLike fun (X : TopCat) ↦ TotallyDisconnectedSpace (↑X : Type u)) ↦ (↑X.toTop : Type u))
              (limitCone (indexFunctor hC)).pt)
        a_1 =
      a
have refine_2 : ∀ (b : (↑C : Type u))
  (hb :
    ∀ (J : Finset ι),
      (π_app (X := X) C fun (x : ι) ↦ x ∈ J : (a : (↑C : Type u)) → (↑(obj C fun (x : ι) ↦ x ∈ J) : Type u)) b =
        (↑a : (j : (Finset ι)ᵒᵖ) → (↑(((indexFunctor hC ⋙ profiniteToCompHaus) ⋙ compHausToTop).obj j) : Type u))
          (op J)),
  ∃ (a_1 :
    (fun (X : CompHausLike fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u)) ↦
        (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u))) : Type u))
      (Cone.pt (F := indexFunctor (X := X) (C := C) hC) (indexCone (X := X) (C := C) hC))),
    (ConcreteCategory.hom (FC :=
            fun (x1 x2 : CompHausLike fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u)) ↦
            C((↑(x1.toTop (P := fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u))) : Type u),
              (↑(x2.toTop (P := fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u))) : Type u)))
            (CC := fun (X : CompHausLike fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u)) ↦
            (↑(X.toTop (P := fun (X : TopCat.{u}) ↦ TotallyDisconnectedSpace.{u} (↑X : Type u))) : Type u)) (X :=
            Cone.pt (F := indexFunctor (X := X) (C := C) hC) (indexCone (X := X) (C := C) hC))
            ((limitConeIsLimit (indexFunctor (X := X) (C := C) hC)).lift (indexCone (X := X) (C := C) hC)) :
          (a :
              (fun (X : CompHausLike fun (X : TopCat) ↦ TotallyDisconnectedSpace (↑X : Type u)) ↦ (↑X.toTop : Type u))
                (indexCone hC).pt) →
            (fun (X : CompHausLike fun (X : TopCat) ↦ TotallyDisconnectedSpace (↑X : Type u)) ↦ (↑X.toTop : Type u))
              (limitCone (indexFunctor hC)).pt)
        a_1 =
      a
Tactic: rsuffices ⟨b, hb⟩ : ∃ (x : C), ∀ (J : Finset ι), π_app C (· ∈ J) x = a.val (op J)