What is wrong with employing foreigners in top positions?

There is an article in the TRE titled, ‘Good work by old guards being
dismantled by LHL’ by a contributor calling himself ‘Disillusioned with
current PAP’. The gist of his post is that too many foreigners are
taking over top jobs in Singapore instead of Singaporeans. And he listed
the following:
 
(1) Magnus Bocker, CEO of SGX

(2) Singapore Botanic Gardens hired Briton Dr Nigel Taylor as