According to the Statisticians’ Manual:

“… the player who first deflected the ball initiated the turnover so is charged with the steal, not the team-mate who recovered the loose ball.”

In the first part of this video, White #11 tries to pass the ball to a cutting #32 near the baseline, the ball was deflected by Red #9 before Red #34 recover the ball. Therefore, Red #9 is awarded a steal (NOT Red #34).

In the second part of the video, similarly, at 0:08, the ball was tapped by White #16 and #23 recovers the ball. i.e. White #16 is awarded a steal (NOT White #23).

Another example, which may be more difficult to judge:

White #5 taps the ball away from Purple #21, who recovers the loose ball, Purple still has control of the possession, thus there is no statistics in this part.

Purple #21 passes the ball to Purple #62, White #11 moves his arms to reach the ball, no foul is called.  White #12 and Purple #21 both try to get the loose ball, which is finally recovered by White #5.

Base on this video, White #11 shall be the initiator for the mistakes (turnover) made by Purple #62. Neither White #12, who only taps the ball after it was loose, or White #5, who recovers the loose ball at last, shall be charged for any steal, since neither player did force the mistake.