Geography , coast formation lesson 101.
Dominant direction of coastline first item, add length of fetch distance between point of origin of swell generating storm.
Lack of intervening land masses or island arc.
Seasonal,variations and prevailing winds, rotational,aspects and seasonal,sizes of the swell,generating storm.
So consider the Indian Ocean no major land masses in its southern reaches between Southern Afric and Australia,
Penetrate a little further south, you have a storm track from Argentina to south of Tasmania.
CircummAntarctic storms , roaring forties and fifties, so as soon as the storm pass the shadow of Southern Africa they begin to propagate swell towards the NE, the islands between the roaring forties and Indonesia present little or no effect on the swell trains.
Swell,decay occurs but great south generates enough power for the swell to reac the entire SW facing Indonesian Coast.
Because the depth of the ocean just off that coast is not made shallow by a large continental shelf. You get good bang for buck and only marginal local refractions and diffractions, the swell is received cleanly.
The southern ocean swell are generated year round and the two seasons of equatorial,and tropical Indonesia give rise to wind response of the monsoons. The Maldives And Sri Lanka are more effected by unfavorable winds as they do not have the relative landmass of the Indonesian Archipelago. And are further north.
Think too, that swells also travel by great circle routes, so huge storms in the Atlantic off Southern Argentina can send activity to Indonesia.
Now consider the Pacific Ocean swell can penetrate deeply frommaround Antarctica even across the equator ( penetrate , means between all the island groups) Fijian and western Pacific cyclone can send cleannswell,to,the west coast of the Americas as can Typhoons from New Guinea to Japan.
Sub arctic storms around the Aleutian island chain and south generate great storms that send swell trains in great arcs southward.
So learn the seasonal,wind variants of any coast stretch you are considering local,storm patterns, mix in pot, form opinion and surf accordingly.

Bear in mind since the early days of surf travel, the viable zones and their most productive has been thoroughly documented and put into forecasts with satellites being able to access the swell,generating potential of a storm and then oceanic buoys able to track the swell,to,specific beaches, you can know before you go! As do the rest of the hordes.!

I've taken up troll hunting just for fun, instead of a rifle I'll just use a pun! 冲浪爷爷