Professor Moriarty's motivations in the Sherlock Holmes movies

The purpose of the bomb was threefold:

1. To conceal the fact that a single person in the room was to be killed


2. To inflame passions in the country's involved to ratchet up tensions for Moriarty's desired worldwide conflict


3. To destroy any trace evidence that any of the above had occurred.

When the explosion is shown from the outside of the building, it is clear that the bomb created a great deal of heat and open flames as well as a powerful explosion. It also clearly destroys all of the windows facing the protagonists. In fact, the room and building should have still be on fire when the protagonists entered given the size of the explosion shown and any human remains should have mangled or destroyed making Holmes' deductions impossible.

The remote control from the first film seems to to fit in with the numerous weapon's technologies been built by Moriarty's vast web of companies. When for some reason the second film's narrative diverged from the ending of the first, the need to explain the remote and how it could have been used (decades before any such device was built in reality) seems to have dropped in favor of telling the new story.