It is a conspiracy theory because you have no hard evidence that JSO is infiltrated and having it's strings pulled by big oil like you claim
It distracts from the fight
No I'd actually argue it brings the fight to the forefront of people's minds, specifically the people who are actually inclined to do something. Those who do nothing but complain about climate activism were never going to do anything useful and so their thoughts on the methods are frankly irrelevant since the methods work for those who actually want to act.
We need these groups to be more self aware and create civil action to get people on board instead of making it unpalatable.
They've blockaded oil terminals and vandalised terrible offenders driving climate change, and still do. It was nowhere near as effective as their publicity stunts, which get people talking. They just ended up getting whisked away by police and largely ignored by the news. Pointless.
Whether you like it or not, the sort of quiet, non-inconvenient activism you seem to be proposing has shown itself to be useless.