Answer by
LeheckaG (1826)
(irs.Gov) Form 1023 Application for Recognition of Exemption
a.k.a. 501(c)(c) "non-profit status"
requires (1) signature (page 12)
by an Officer, Director, or other-authorized-official.
Some other forms often require (2) signatures to lessen fraud by individuals.
Fraud by (2 or more) people is a conspiracy,
and then government has more legal tools at their disposal
to investigate and prosecute such conspiracies.