In a very short space of time UK tourism to Sharm has reduced from 2,000,000 to 1,000,000,
The missing UK numbers have been replaced by Russian tourists, it would therefore not be of any benefit to the Egyptian locals to upset the Russians and they still love the UK visitors who have continued to holiday there.
The Russians have recently "assisted" in the bombing in Syria of (ahem) ISIS positions.
ISIS, IS or ISIL really don't give a about who they upset.
ISIS, IS or ISIL are not shy about claiming responsibility for this type of incident.
Therefore ISIS planted a bomb and are keeping shush just in case the Ruskies actually level Syria in a fit of pique.
The Russians however are still stating that there is no evidence of a bomb.