Uhm...... why are you directly comparing the current time to a previous one?Black people (generally) find English easier. Why? Because their families and friends already speak it so they get more exposure to it growing up
Even if you could somehow objectively prove that Afrikaans in and of itself is easier than English, it makes no difference to somebody that grew up with English around them. That exposure alone will make English easier to them than Afrikaans.
At the time..... how many blacks were as in your words "already speak it so they get more exposure to it growing up"?
Did the English majority thing not specifically happen as a way to politically counter Afrikaans?