God was leading the Israelites down the longer but safer route, even if they didn't know it. His directions must have seemed strange, but there was great wisdom behind it.
God knew His people and how they would have reacted to the war that would have happened if they went the "easier" way. Just because they had been saved doesn't mean they were ready to handle every trial before them.
God also knew Pharaoh's heart, and would bring Himself glory and show His power by leading His people in a wandering way. Pharaoh's heart was hardened and they were realizing that without the slaves they would need to do all the work. This reflects how Satan/sin will never let you go while you're on this earth. God fights for usso that we can persevere.
Pharaoh was so depraved it is as if he had forgotten all about the plagues they had just suffered through. The Israelites also had short-term memory as their cried to God were in fear and not in faith for the Lord to deliver them as promised.
There are those that idealize those at top like Pharaoh and those that idealize the underdogs - we must remember there is madness on both ends. Don't go into a ministry of helping the underdog for personal glory or quick results.
God alone would be able to save His people, there was nothing they could do against Pharoah's army. He makes a way for us. Sometimes we must just go instead of delaying in prayer. God reveals His sovereignty over nature by parting the sea. Before the Egyptian army was destroyed be the sea, the Lord already defeated them and caused them to panic. The army's death in the water could have been a reflection of the Israelites' babies being slaughtered before.
Moses told them not to fear man, but to fear the Lord. They were to trust in God and give Him praise.