Please let us explain this. Visa applicants are able to request multiple entry for 1 year when submitting visa application. However, the result of the visa issuance is the right of the embassy (even though you previously had 1 year multiple entry).
We would cordially inform you that we had tried to enquire the reason but they did not inform us any information so that we did not know their reason as this is personal & confidential matter of the traveler/ visa applicant; the Singapore embassy will inform you personally if you contact them directly.