But why the hell not, I'm bored. Here's my google-informed take.
1 - I don't know why you would suggest that modern scientists and doctors are "not as smart as their predecessors." If anything, they're better informed than their predecessors, which is not really the same thing as smart. If you're suggesting that a scientist from 100 years ago would have been faster to develop a treatment or a vaccine, that's ludicrous.
2 - The biggest reason is the communicability of this virus. With H1N1, some people are contagious for 1 day pre-symptoms. SARS is generally only contagious when you have symptoms. With COVID-19, you can be contagious for a week or two and not know it. Some people have the virus, never have symptoms, and walk around for who knows how long potentially spreading it. Zika is spread by mosquitos, that's completely different. Ebola only spreads by body fluids - it's very dangerous to you if you're caring for an Ebola patient, but otherwise not. AIDS is similar in that way, you can be in close daily contact with an AIDS patient and never catch it, unless you're sharing body fluids.
All of that is the reason for social distancing. If you gather in a group (class, church, bus ride to marching contest, whatever) there could be someone in the group with no symptoms who nonetheless can infect you. The more people in contact with each other, the faster it spreads.
3 - depending on your political leanings, either Trump or China. I think it's just a case of evolution (of the virus) outpacing medical technology. Realistically, I don't know that we'll ever know the entire picture.