Once he made the 2nd tx then the first tx was effected because it had its input and output same address. And as a reason the first Tx dropped?
So the first transaction dropped because the second transaction spent the same input as the first transaction. Once it was spent by the second transaction, it was no longer available to be spent in the first, and so the first became invalid.
Even although the 1CKnh... address still had enough funds on it for the first transaction, they were now part of a different output, and so the first transaction was still invalid. Transactions spend specific outputs. If I have an address with 5 outputs each of 1 BTC, and I make two different transactions using the same output, only 1 will confirm and 1 will become invalid, even though there are 4 other outputs of 1 BTC at that address.