There are several factors that play into this:
Responsiveness to calls: The big draw of these ads is the ability for prospects to call an agent directly from the ad unit. Naturally, then, if an agent does not pick up phone calls, Google will deprioritize the agent’s ads.
“Google Screened” badge: Google gives priority treatment to ads that have a “Google Screened” badge. “Google Screened” agents will rank higher and appear more often in search results.
Budget: Local Services Ads are a paid product. The more budget an agent commits, the more likely Google is to prioritize his or her ads.
Reviews: Google reviews are the ultimate social proof. They are viewed by many homebuyers and sellers, particularly millennial ones, as more reliable than any other advertising or marketing channel—including referrals. The more up-to-date (within the past 90 days) reviews an agent has, the better.