During physical activity, you sweat, and if you do not rehydrate yourself, you just get more and more dehydrated. Joseph also had to play multiple positions due to the lack of players, and the temperature outside was high. He then consumed multiple energy drinks which contain caffeine (this dehydrates you even more). This led to his muscle cramps.
Question 3: Since you lose a fair amount of sodium in your sweat (hence the salty taste of sweat) You are losing a neurotransmitter and an electrolyte that is crucial to muscle contraction. Since both the sodium and potassium gates opening at the same time creates end plate potential and that stimulates an action potential in the muscle, if you are missing sodium and the gates open at different times due to the uneven flow of the neurotransmitters, this causes an imbalance that leads to cramping.
Question 4: FIrst of all, caffeine is a diuretic, meaning it increases your need to urinate. This further dehydrates you, although not by that much. Regardless, caffeine increases your synaptic transmissions, giving them a sort of turbo boost. SInce you are already dehydrated and missing your sodium, this makes the imbalance in the gates opening even greater which just amplified the effects of his