Why was Hegseth using Signal to discuss military strategy?

Source

Here's a summary:
A journalist learned about the U.S. bombing of Houthi targets in Yemen two hours before it happened when Pete Hegseth, the secretary of defense, texted him the war plan. The situation stemmed from Houthi attacks following Hamas’s invasion of Israel in October 2023, with the Biden administration failing to respond effectively and the incoming Trump administration preparing a stronger approach. The journalist was unexpectedly added to a Signal group chat that appeared to include top U.S. officials discussing military plans. Initially suspecting a hoax, he became convinced of the chat’s authenticity as it contained detailed attack plans that were later executed as predicted. The incident raises serious concerns about national security and information security at the highest levels of government.

List of People in the Signal Group Discussion:
Michael Waltz (presumed Trump’s National Security Adviser)

Pete Hegseth (Secretary of Defense)

Marco Antonio Rubio ("MAR") (Secretary of State)

JD Vance (Vice President)

Tulsi Gabbard ("TG") (Director of National Intelligence)

Scott Bessent ("Scott B") (Treasury Secretary)

Dan Caldwell (Representative for DoD)

Brian McCormack ("Brian") (National Security Council)

John Ratcliffe (CIA-related discussion participant)

Steve Witkoff (Trump’s Middle East and Ukraine negotiator)

Susie Wiles (White House Chief of Staff)

"S M" (presumed Stephen Miller)

This group allegedly discussed military strategy, the timing of the attacks, and geopolitical consequences, all in an insecure messaging platform, making the leak of such information a major security concern.

Theories:

^{The Government is behind Signal and reads everything on it.}

It seems unlikely that top U.S. officials would use Signal for sensitive military discussions when secure government networks exist. However, there is evidence suggesting Signal may be backed by the U.S. government. The app has received funding from the Open Technology Fund, which is linked to the U.S. Agency for Global Media. U.S. intelligence agencies have previously funded encryption projects like Tor, raising questions about their role in Signal’s development.

or

^{The current administration is using it to avoid leaks (though they inadvertently created one while trying to avoid it.}

The Trump administration’s use of Signal might come down to distrust of official channels, worrying about leaks or surveillance. This isn’t new—past administrations have used backchannels, but Trump’s team took it further. Reports suggest they avoided government-issued devices and relied on private emails during the transition, likely to keep discussions away from prying eyes.