Serious question: Why do SCOTUS confirmations take longer than they used to? (even before Garland)?

Ford nominated John Paul Stevens,
he was confirmed in 19 days.

Reagan nominated Sandra Day O'Connor, she was confirmed in 33 days.

Since O'Connor, everyone has been way beyond 33 days. (Ginsburg was 50 days, and the rest were 60, 70, 80 days you get the point… Elena Kagan was 87 days)…

(unless you count John Roberts at 23 days but he nominated for "Associate Justice" then withdrawn and then re-nominated "Chief Justice" so technically it was 62 days total)

Were Stevens and O'Connor not vetted thoroughly?
What changed? They just one day woke up and decided "hey, we need vet them better"?

Added (1). 1975 - John Paul Stevens was confirmed in 19 days.

1981 - Sandra Day O'Connor was confirmed in 33 days

1986 - Antonin Scalia was confirmed in 85 days.

What changed during the 80's?