Linked from
The 9 pages that link to Muon decay, each with the reason it gives.
Weak interactionBroader topic: It is a purely leptonic example of a W-mediated weak decay.
W and Z bosonsRelated: A virtual W boson mediates the decay.
MuonBroader topic: This is the muon’s characteristic fate and sets its finite lifetime.
Charge conservationRelated: The charged daughter has the same electric charge as the parent muon.