intervening play

[_Bruno_]

i still don't get this intervening play thing.
we have R3 and R1, 0 outs.
F6 fields the groundball and goes for the force to F4 at 2nd but R1 beats the throw. now R3 steps on homeplate. R1 now intentionally slaps F4 on his throwing hand, so he cannot complete the throw to F3. we call R1 out for the interference, put BR on 1st and send R3 back to 3rdbase. so far so good.

why isn't the try to force R1 at 2nd not considered an intervening play ? i mean, the play was to force him,they didnt make it, and the throw to 1st was the following play. is it because the player they made a play on (intervening play), made the interference ?