More could be written, but you might like to see these previous discussions:

"Why did the seafarers from Borneo colonize Madagascar and not places closer to their origins?" by /u/Prufrock451 , though with some objections by /u/l33t_sas that were not answered.

"How was Madagascar settled? How were Pacific Islanders able to sail so far on such small canoes?" , in which /u/khosikulu basically agrees with Prufrock451.

"Why didn't the Polynesians colonize Australia?" , by Algernon_Asimov and cahamarca.

Some links are from Searocksandtrees's reply here . (I checked the other links there, but I think the above cover it sufficiently.)

This is not to discourage discussion. More questions, data, and debate are welcome.