Sure, but in real life soldiers don't make those kinds of calculations. Most medieval battles only lasted a few minutes before one side or the other panicked and ran and then the other side murdered them as they retreated. It's not rational but it's a normal human reaction and those dudes didn't have a 50 foot long fire breathing monster coming at them.
I had this same reaction, but as you can see in Xarpolis' picture above, whoever tackled him was actually on a horse next to him. I had thought Bronn tackled him from the ground which would have been impossible at a full gallop but either Bronn found a horse real fast while Dany was tugging on that spear or someone else saved him, possibly that Dickon guy who saved him earlier.
Next week speculation:
Jamie and Bronn are alive, but will probably be captured and possibly switch sides.
Drogon is not seriously injured. Giant crossbows are not useless, but hardly the answer to dealing with dragons
Tarly is not dead. I just think they spent too much time with his character to just have him randomly get killed in battle and not even show it. Probably going to be some sort of redemption scene for Sam involving him.