That paper literally only looks at the time frames and attributes positive things from mask-wearing. Sounds about what I'm hearing on the media i.e. correlation and speculation.

Also this:

The authors rightly note that other community-wide and hospital-specific interventions may have contributed to their observation, including the statewide declaration of emergency (March 10), new hospital policies to restrict visitors (March 12) and elective procedures (March 14), statewide school closures and hospital restrictions on business travel and on-site working (March 16), local public transportation reductions (March 17), issuance of statewide stay-at-home orders (March 24), and automation of screening and testing (March 30).