To begin with, after the seal was broken on the No. 1 debut in 1995 (by Michael Jackson's "You Are Not Alone"), there were ten No. 1 debuts between 1995-1998 -- not simply because there were suddenly that many instantly massive chart-topping smashes, but because labels began to realize that they could make more of an impact on the Hot 100 by waiting to release the physical single of a song. Once they had already accumulated enough airplay, a one-week sales boost (maximized by pent-up demand from a delayed single release) could send it straight to No. 1, and in the meantime, single sales wouldn't eat into more-profitable sales of the song's parent album.
However, this strategy only worked for the period where Billboard's rules for the Hot 100 stated that a song must have a physical single release to be eligible for the chart. In late 1998, those rules were done away with, allowing songs to chart on airplay alone and essentially eliminating No. 1 debuts on the Hot 100 for nearly a half-decade in the process. Then, from 2003 to 2006, another four songs debuted atop the chart -- a rate of exactly one per year, as those debuts all came from the debut single releases of the winners from the competitive reality TV phenomenon American Idol (or in the case of Clay Aiken in 2003, the runner-up). Those artists' debut singles were released quickly after their crowning, and drew such blockbuster sales that airplay was practically irrelevant in their chart placement.
Following Idol's slide from its peak popularity, there was again a multi-year gap in No. 1 debuts -- until iTunes' download numbers began to peak at the turn of the decade, resulting in another six much-anticipated new singles from superstar artists debuting at No. 1 between 2009 and 2012, largely off such digital sales and week-one airplay. And this time, there was no long period without debuts atop the Hot 100 to follow, since just as those iTunes downloads were starting to taper off at mid-decade, streaming began to rise in its stead, and was added in fuller force to the Hot 100 calculation formula -- once again allowing songs by big-name artists to achieve mass consumption immediately. Since 2009, there hasn't been a single calendar year that hasn't seen at least one debut at the chart's pole position.
However, 2020 is still proving to be highly exceptional, even for the streaming era. In 2018, there were four debuts atop the chart (tied with 1995 for the most in a year until 2020), and in 2019 there were just three, compared to nine already this year, with nearly three months still to go. What's different this year? The biggest change would likely be the re-introduction of physical sales as a major factor -- collectible items marketed by star artists to rabid fanbases more interested in the merchandise aspect of a physical single release than as an actual way to listen to the song.
Pop stars have gotten more and more creative with such direct-to-consumer (D2C) content, with artists like Scott offering as many as 15 different physical configurations of new songs for fans to purchase, allowing for greater first-week impact, particularly in an otherwise mostly depressed digital song sales market. (Such releases have usually been paired with a download, although per a recent chart rule change, any physical single sold with a digital download will no longer be counted as a digital sale and will only be counted as a physical sale upon its subsequent shipment to purchasers.)
A greater number of surprise and/or event releases this calendar year has also helped contribute to the surfeit of No. 1 debuts. You may notice from the list of the nine such debuts that seven of them are collaborations -- big-name team-ups between star artists, some with already-established successful partnerships (like 6ix9ine and Nicki Minaj) and some with first-time heavyweight linkings (like Lady Gaga and Ariana Grande). Such collaborative releases often have a multiplying effect on first-week numbers, as fans of both artists come out in full force on debut week -- not just to hear the highly anticipated new song, but to actively support their faves on the charts, rooting them on like a sports team. And the two that came came from solo artists were also events in their own right: Taylor Swift, one of the biggest pop stars of the 21st century, releasing her first surprise album (with "Cardigan" its lead single), and BTS, likely the biggest pop group in the world right now, releasing their first English-language single in "Dynamite."
Also clearing the way for these No. 1 debuts: The lack of enduring cross-metric smashes this year in general. After all, there might have been five or six extra No. 1 debuts in 2019 without the historic 19-week reign at No. 1 of Lil Nas X's Billy Ray Cyrus-featuring "Old Town Road" blocking all of them from the top spot. There hasn't been a song like that clogging pole position for so many weeks this year -- in fact, aside from a pair of Roddy Ricch hits (his own 11-week No. 1 "The Box" and his featured appearance on DaBaby's seven-week chart-topper "Rockstar"), no Hot 100 No. 1 this year has reigned for longer than four weeks.
That's in large part because radio and streaming are out of sync in the hits they're pushing -- only The Weeknd's "Blinding Lights" has topped both Billboard's Radio Songs and Streaming Songs listings this year -- and because no song since "The Box" is dominating streaming at the level of an "Old Town Road," or even a "Despacito" (from 2017). That allows a great deal of opportunity for turnover at the top -- indeed, the 17 No. 1s we've seen so far this year have already passed last year's tally of 16 total Hot 100-toppers (and are the most in a year since 2010) -- since not many singles are enduring long and strong enough to keep the bar of entry for a No. 1 debut particularly high.
Is this just the new normal for the Hot 100's top spot? Perhaps, though if history has taught us anything in this respect, it's to not expect this or indeed any chart trend to just continue indefinitely; sooner or later, some change will come that alters a key variable in the race for No. 1, and mucks up the whole equation. Regardless, one thing is for sure: Artists will always want the chart cachet and easily understood triumph that comes with a Hot 100 No. 1 debut -- and chances are, no matter how the code changes for landing one in the years to come, the biggest (and smartest) stars will continue to find new ways to crack it.