Not all non-profits, just 501(c)3. Non-profits organized under other sections of the tax code are allowed to be political. [0] Here's an exhaustive list. Some of the sections are pretty narrow in scope (e.g. 501(c)(21) - black lung benefits trust). [1]

[0] https://www.thebalancesmb.com/can-nonprofits-engage-in-polit...

[1] https://www.thebalancesmb.com/how-the-irs-classifies-nonprof...