It's a huge deception, The Saudis and the US are ISIS. The only people truly trying to destroy ISIS are Russia & Syria with a bit from Turkey however they've only recently done a 180 when the saw the tide was turning towards Assad once Russia piled in. The majority of properly organised Jihadis have always been funded & trained by either the US or their proxies and used to topple whichever regime wasn't towing the line. Getting to your question, is it strategically wise? No, it's a shit idea however they don't have choice, they either double down or go home. It's going to end really badly for Saudi as the US will throw them under the bus when it's obvious it's over. They've been doing the same stuff for years.