It does make sense for russia (or at least Gazprom). They've cut deliveries through the gas pipelines anyway. Now they might have needed a reason not to pay penalties for contract violation. By blaming random terrorists or the US they can claim technical issues beyond their control.

While I wouldn’t say "most of the world", it’s certainly not "few doubt that the Kremlin did it" either.

I think most people assume Putin blew up the pipeline to limit the possibility of his would-be successors being able to sell gas/oil to the West. And Putin has probably rigged the other pipelines with explosives. Otherwise the incentive is too strong: someone in the FSB or the military could kill Putin and start selling unlimited amounts of oil/gas to the West. Putin is well aware how easy life is going to be for his successor, unless he takes steps to limit their options.

It shows that he is willing to cross (another) border we didn't think he would cross. The motivation is to cause fear, uncertainty, and doubt in western countries, lowering support for Ukraine. Here in Norway we are definitely more worried than we were before, so that part of it is working. Will it help him split the west? Will more and more people speak out against supporting Ukraine? Fear can be a powerful motivator. Time will tell.