Hezbollah's scale works against them here. The problem with the pagers was they needed to buy so many of them (3000!) that it was effectively impossible to source them quietly and anonymously within the local economy. Instead, they had to act like a bureaucracy, putting out solicitations and ordering in bulk from suppliers. This exposed them. The seller (Israel) was able to react, attract their business, and deliver rigged devices as part of what appeared to be a normal business transaction.