To stent in a multi-vessels on the same vessel can change the hemodynamics of the vessel segment involved and affect blood flow to other areas. A by-pass may bridge more than one lesion, and there will be a different dynamic and possibly a more favorable expectation.
There is a need to assess whether there may be a surgical problem for surgery based on weight and diabetes could be another consideration and there can be a problem with healing for diabetics.
It depends on many things for a stent being possible. Firstly, if the occlusion is hard, as in solid plaque, it can be impossible to get a catheter wire through it to the other side. This would involve 'chipping' away at it producing a risk of losing pieces of plaque to lodge in small vessels in the heart or brain. If the occlusion is on a curve this can also be a much higher risk because as the catheter goes through the occlusion it can end up through the artery wall on the other side.
The occlusion I had removed at the top of my LAD was 30mm long and the first 10mm was solid plaque. The occlusion was on a curve and the start was right on the very edge of the circumflex branch. It took 5 stents to clean up the artery and I think the cardiologist performed a small miracle. I saw 12 other cardiologists and they all said it was either impossible or too risky. Finding a very confident cardiologist due to experience can be difficult. My cardiologist has been doing stenting for over 20 years now and is seen in the UK as the stent king.