In the American body of law and legislation, strikes such as these aren't illegal. Honestly, we've been doing stuff like this for decades.

Did it surprise you when Obama did the same?

He didnt?

Are you sure? He certainly engaged in a lot of military operations in several countries without Congress's approval. He also ramped up drone strikes dramatically.

Not to justify what Obama did, but that all fell under the post-9/11 "War on Terror" AUMF.

None of those required congressional oversight. The US hasn't officially declared war since WW2. That's largely due to every administration since then finding clever wording to get around it. Did Obama do unethical things? Probably, geopolitics is not a game of right/wrong. Did Obama do anything illegal, nope. Same with Trump. (Yes, in this context I'm both-sidesing, but not every context: Trump wants to imprison/deport/kill me and people I love, there's no comparision, and he's too dumb to be a nazi but is absolutely an evil dictator. Obama never put crosshairs on the heads of US citizens for not being straight white christians or not kissing his ass.)

Because acting unsurprised means giving Trump a pass. It means normalizing awful things and normalizing hate and hurt. No one actually wants the world where he has no moral limits.