The problem with that theory is that the methane released from the ground wouldn’t smell like rotten eggs. Natural methane is odorless, they have to put the “rotten egg” smell into it with an additive, otherwise nobody would notice if they had a gas leak.
Well, sulfur smells like rotten eggs, and that does come back around to an earth-shifting scenario.
Smells can travel a long way though - when the big forest fire happened in TN awhile back, we caught whiffs of forest fire all the way up in central AP (it did smell like what it was though, burning forest).
H2S is a common hazard on offshore oil rigs. You can smell it coming, and it smells like sulfur, or rotten eggs.
SoCal is still floating on a sea of oil. There is a permanent slick off the coast down there, attributable completely to the natural seepage of oil from cracks in the floor of the ocean down there. Coast Guard gets complaints about it all the time from people who don’t know that.
There was a case of a lake in Africa that killed two entire villages due to outgassing - first of methane, then H2S.
The methane killed many in their sleep - it’s odorless. The H2S made recovery teams it was the bodies rotting that caused the smell. The found out differently when some of them started passing out from being overcome by methane.