Maybe today it doesn't with streaming. But back then it surely did. If radio airplay had no influence on sales, then record labels were stupid for spending all of that money on payola for decades since the 1920s or whenever.
You really think
Thriller would have sold what it did without radio airplay? It was no accident that Clive Davis specifically chose songs for Whitney Houston so that she would get mainstream Top 40 airplay to get the bigger sales unlike Millie Jackson, Regina Belle, Stacy Lattisaw,, or Betty Wright who just got R&B airplay. That's why there was a singles chart. Before the internet, the singles chart tracked radio airplay & sales of 45s. Album tracks that got radio airplay could not chart on the singles charts in the USA. Nobody bought a 45 of those. Even the rock bands that didn't get much Top 40 airplay like Pink Floyd & KISS were played on the AOR radio format they had back then.
If radio airplay has little influence on sales, then how come music that isn't on commercial radio don't get huge sales like jazz, polka, zydeco, gospel, bluegrass, opera, barbershop quartets, etc.? Or acts on small indie labels instead of majors? People would just buy that stuff in the same quantities as Journey & Bon Jovi, who did get heavy radio airplay. Milli Vanilli sold multi-platinum because they were on the radio. Notice that Lionel Richie was way more successful than the Commodores were after he left. They only really had 1 big hit (
Nightshift), other than that they didn't get the airplay even on R&B radio. But both Genesis & Phil Collins got a lot of Top 40 airplay. So they were both successful. Pop radio pretty much ignored the
2300 Jackson Street album, but it got R&B airplay.
Also just because one act is popular does not mean everything they do will be, or else Ringo Starr & John Lennon would have sold as well as The Beatles. Paul was the most successful solo Beatle, not the other 3 so much except on certain records. John probably had the least commercial records or the 4, None of the solo records of The Rolling Stones were really successful, but the band itself is still popular today on the touring circuit. I doubt a Mick Jagger solo tour would make anywhere near the same amount of money.