Trump's presidency challenged traditional wisdom about the amount that experience, whether political or military, matters to voters in a Presidential candidate.
Trump's election proved that a political outsider can be appealing to voters. Steyer has never held elected office, and therefore is uncorrupted by years of being in the trenches of Capitol Hill.. He will not have to bow to anyone for fear of upsetting D.C. insiders. His experience as a businessman will enable him to confront Trump head-on. He is not 'all politics' - he is real. He has the resources and funds to run a campaign, despite his outsider status.
Being an outsider is not necessarily an advantage. Being a billionaire outsider may not be appealing to Democratic voters at a time that many are calling for dramatically increased efforts to fight inequality. Additionally, typically political experience helps candidates, particularly Democratic candidates. He also does not possess the name recognition that has helped Trump.
[P1] Steyer is a political outsider. [P2] This will appeal to the voters as political outsiders become increasingly appealing.
Rejecting the premises
[Rejecting P2] Political outsiders are not necessarily appealing to voters.