At this point, it looked like they would catch Moses. It looked bad. This would be the time for the Israelites to hold onto their faith that God would deliver them. It was very tempting at this point to fall into fear, rather than stand in faith.
But the Lord looked down and threw the Egyptians into a panic. He took off their chariot wheels, so that they moved with great difficulty. (Imagine driving a car with no tires.)
At this point, the Egyptians realized, “The Lord is fighting for the Israelites against us! Let us flee from them!”
Then the Lord said to Moses, “Stretch out your hand over the sea, that the waters will come again upon the Egyptians, upon their chariots, and upon their horsemen.”
We know what happened. The waters covered the Egyptians and they were killed.
God could have just flooded them in mid stride, without taking off the chariot wheels first, but I believe He wanted them to understand that they were stuck. The chariots that they had trusted in were not strong enough to fight against God’s will.
If God had merely flooded them, they would not have had the opportunity to repent; they would have been merely washed away. God gave the Egyptians a small window of time to see what they did was wrong.
The Lord took off their chariot Wheels so they had time to think about what they were doing and to see that it was against His will.