Here is how I explain it:
Be sure to read this with an open mind, even if math scares you, it is only basic addition which I believe anyone is capable of understanding. Enjoy.
I like to use what I call the practical lift formula, that formula is Lift = Speed + AOA. It is nothing more than a general method for seeing how Speed and AOA work together, increase one the other must decrease to maintain the same lift.
Let us assume we stall at 17 degrees, since Va is related to the amount of deflection we are allowed let's say that we must be at or above 7 degrees for us to be at Va. If we are at 7 degrees we will have a safe amount of deflection, in reality these numbers also don't work but are used here merely for demonstration purposes.
Input some numbers, now these are also unrealistic but will unquestionably demonstrate the relationship with weight and Va.
Aircraft one: Weight = 20 which means Lift must equal 20 to support this weight, remember lift equals weight.
Apply practical lift formula: 20 (Lift) = 7 (AOA) + 13 (Speed)
Aircraft two: Weight = 22, again Lift equals 22 to support that weight.
Apply practical lift formula: 22 (Lift) = 7 (A0A) + 15 (Speed)
Conclusion: At the heavier weight of 22 the speed was able to be 15 instead of 13 at the lighter weight. Obviously these numbers aren't logical, but who cares? They serve the purpose of showing, with an obvious, easily understood, representation that with a heavier weight we can attain a faster speed with the same AOA and thus a faster maneuvering speed.
Disclaimer: I purposely annotated each formula with () to show which each field was. This was done for simplicity with regards to the reader. Since many people don't like math because there are numbers that don't represent meanings this depicts the meaning clearly next to the number.