Some people in California may have those mailboxes, but not most people. I'm very much in the city in a house built in the late 70's and here are the mailboxes in front of my house in San Diego.100 landings, sets of steps, right next to a door. Very doubtful. Very risky for being seen in the time to go door to door to 100 houses.
The entire housing tract has mailboxes in clusters of 4 exactly like this. In newer housing developments they have far bigger cluster mailboxes.
My comment on mail fraud isn't limited to that one guy they found passed out with 300 ballots. There are hundreds of guys like that. What I'm trying to communicate is that there is an industry of stealing ballots and submitting them. It wouldn't work for my ballot because I had filed to vote absentee which means the registrar of voters has my email address and sends me a confirmation. I can even log in and see how I voted.
However, there are a large group of senior voters who like to vote in person. When COVID hit, California changed so that everyone was automatically sent ballots including those voters who always vote in person. For those voters, the registrar of voters doesn't have their email address and doesn't send notifications. They wouldn't know someone had stolen their ballot from their mailbox and submitted it for money until they showed up to the polling place to cast their vote only to be told they'd already voted.
Mail theft is a felony, but this type of ballot stealing wouldn't be a thing if ballot harvesting weren't legal. In California, anyone can submit anyone's ballot without needing to identify themselves. Super-Republican Orange County went from reliable Republican to having every single Republican lose to a Democrat challenger as soon as universal mail-in balloting became a thing. If you want to believe the elderly woman in the news article wasn't telling the truth about the polling place telling her she'd already voted and that this kind of harvesting isn't happening then I can't stop you, but I don't agree.