This was probably because Thondaman was a politician and not a trade union activist
One occasion when Thondaman showed his prowess was when he crushed a rebellion with the congress
Thondaman had a bigger role to play than sticking merely with the Tamil Estate labourers’ salary issue
The death of Minister Arumugam Thondaman (56) a few days ago is sure to affect the struggle of Tamil estate workers to survive the 30 days of the month. The living conditions in tea estates is appalling to say the least. The late minister was part of discussions with plantation companies or Gotabaya Rajapaksa; when the latter was bidding for presidency last year, in attempts to raise the living conditions of estate workers.
Whether he was successful or not in attempts to obtain a decent daily wage for workers is debatable. There were of course unions , backing the workers, which had clout; sometimes showing more promise than the minister when batting for these hapless plantation workers.
http://www.dailymirror.lk/opinion/Arumugam-Thondaman-A-struggle-left-incomplete/172-189432