Most states (and all federally backed mortgages) have temporarily suspended evictions so the short answer is that people in financial distress dropped that expense, which is usually the single largest on most people's budgets (for low-income people this can often be 50% or more of take-home depending on the city - yes, the rule of thumb is that it shouldn't be higher than 25% but you simply can't find affordable housing in a lot of areas).
However that one eventually is going to come due because the federal mortgage eviction moratorium doesn't prevent you from going in default on your mortgage, it only prevents evictions. The 3-month timer is still running and as soon as the moratorium on evictions is lifted, they can kick you out immediately. So as soon as that lets up in a month or two there's going to be a massive surge in evictions in states that do not go out of their way to keep evictions suspended.
(and in fact this is probably a snowballing problem, the longer this crisis goes unchecked and the worse the economic pain gets, the more people that will be in default and the bigger the difficulty of getting "back to normal". Furthermore at some point that shit starts rolling back uphill economically, banks turned your mortgage into financial products and you not paying is cutting off the income of someone else, and in fact there is an eventual risk of a 2008-style crisis occurring on top of all the current problems if we get into a situation where people are defaulting en-masse.)
