That's a big factor. But there are a bunch.Because they're overloaded for pacers to end things quickly. Because of pitches being prepared that way. Some people fail to grasp this however.
Swing is responsible for a ton of wickets in RSA.
Pretty much every team has had really good bowlers and iffy bats recently. RSA more so than anyone else, and they are 50% of innings in RSA.
Batting SRs have gone up a lot recently. This is particularly true of RSA bats. They were crazy slow at the start of Kumble's career, and are very fast now.