Dumping Flynn looks weak and will encourage the left to go after more scalps. And the people that were after Flynn are seeking war with Russia and Syria. War is easy, peace is hard, for it is always easier to create disorder than maintain order.
But, on the other hand, Flynn was expendable. On studying his career, I find he was a neocon, and an advocate of Coin (counter insurgency warfare). There is no such thing as counter insurgency warfare. There is only warfare. The stronger force wins, the weaker force loses, unless a large outside power (the Soviet Union or the United States State Department) has its thumb on the scales. In warfare, you don’t worry all that much about hearts and minds, for if you have to choose between being loved and being feared, you choose to be feared. If choosing to be loved was a realistic option, it would not be war. It would be social work.
If every time someone shoots at you from a girl’s school, you incinerate the school with girls and teachers inside, people stop shooting at you from girl’s schools. Or, more likely, the girls decide to skip attending school for the duration of the war.
The reason the Taliban has defeated the US in Afghanistan is that the US forces are infested with lawyers, the political commissars of the State Department, while the Taliban is not. The Taliban has the close equivalent of lawyers, priests, but their priests are interested in winning, they are warrior priests, while the State Department, the Blue Empire, is more interested in defeating the Pentagon, the Red Empire, than defeating the Taliban. If one side is fighting by police rules, and the other fighting by warrior rules, of course the warriors will defeat the police.
So quite possibly Trump initially chose Flynn as a compromise candidate, to sooth his enemies until his Pentagon powerbase is more secure, and is merely ditching him earlier than planned.
The hard core Trumpist position is that Russia should be allowed to be Russia, rather than being forced to accept progressivism, but Muslims should be smacked around till they stop making war on us. To get the Pentagon behind this position, he needs to do a Grenada – decisively defeat some penny ante bunch of Islamic extremists, preferably in cooperation with Russia. Maybe set up safe zones in Syria with the cooperation of the Russian and Syrian government.