How about a super secret sci-fi cloaking suit...oh wait a minute, Starfleet already has them...How else would the spy get aboard Picard's ship? It's two-birds-with-one-stone tactics here, as Picard's ship now also becomes the one closest to Romulus. It was actually pretty clever, down to drafting the aid of locals to keep Picard from stopping to think...
The entire Senate except for Tal'Aura were killed by the Thalaron weapon. Also I doubt a major power such as the Romulans would have flourished if assassination and coups were commonplace (political manoeuvring and secret agreements between delegates definately, but they aren't murderous savages like the Klingons).I doubt Shinzon "waited". He had just conquered Romulus - surely there'd be quite a few odds and ends to take care of. Such as stopping the next six clowns in the line from repeating the feat, as palace coups probably happen every Tuesday on Romulus.
He could have at least dispatched a couple dozen Reman Warbirds to escort the E-E to Romulus and then maintain position around her until he was ready to meet with Picard and co.
Forget the Romulans then, the Remans followed him. They may have their own ships, or could easily board Romulan ones and take control, thus giving Shinzon a small fleet to command.Shinzon didn't really appear to control much - the only other Romulan vessels we saw chose to oppose him. And a plan to attack the Federation was just what he had promised to his Romulan backers, not what he personally wanted.
Why Earth? If I was the clone of a human officer, created by Romulans, then discarded to Remus, where I was beaten upon frequently and hated by the Romulan guards, I wonder who would be best to strike at? A planet that means little to me or the homeworld of the people that made my life a misery from thevery day I was created. Hmmm, decisions decisions.More specifically, the plan was to destroy Earth for no reason. Apparently either because Shinzon was batshit crazy - or because that was the full extent of his amazing Spartacus superpowers (just one ship, just one exceptionally short life), and he could never hope to achieve other kinds of victory, so why not go for something flashy (i.e. he was batshit crazy)?