It helped that Bera tends toward the center-left, with a business-friendly bent. (“Organized labor does not like Bera and neither do we,” the liberal group Progressive Scorecard asserts in giving the six-term congressman a thumbs-down rating).
Stutzman, for his part, is no longer as socially conservative as he once was. (After running a 2000 campaign to ban same-sex marriage in California, he has long since renounced that position.)
It also helped that both are self-described institutionalists: people who fundamentally believe in our government and political system and want to see them function better than they have in recent years.
Which means more maturity and pragmatism and less performative bombast and schoolyard antics.