In the case of a delayed block creation, this is because bitcoin is built around randomness and every block is created randomly in different time frame mostly.
Averagely, each new block is created for about 10 minutes, sometimes it can be earlier or after.
These orders are piled up in the Mempool and transfer fees increases upon the creation of a new block.
Transaction fees do not increase upon the creation of a new block, transfer fees increases due to mempool congestion or fee competition among senders.
Users with low transaction fee would get stuck in this mempool as miners would process high transaction fees first.
Yes, this is correct. Miners will prioritize those paying higher fee than the average or those minimizing fee cost.
3. The exchange failed.
It is just a delay caused from creating a new block to accommodate pending withdrawals in the bitcoin cycle.
Exchanges often place withdrawals on batch, that may be a cause for little delay.