This article was published while now PM Mahathir was in...

This article was published while now PM Mahathir was in opposition. Certainly gives an excellent summary of his thinking at the time which was certainly not anti Lynas.
http://www.themalaysiantimes.com.my/mahathir-agrees-with-government-on-lynas/

Dr Mahathir this week spoke in London on his ambitions for a motor vehicle industry in Malaysia. Seems he also met privately  with Dyson. Be very interesting to know what was on their agenda. Dyson currently developing electric powered vehicle. Any chance an assembly plant to be established in Malaysia? What an opportunity for Lynas, a local manufacturer of NdPr  to establish a JV to manufacture PM in Malaysia, possibly with Japanese partner? Maybe I am pushing the strategy envelope too far?
https://www.nst.com.my/news/nation/2018/09/414561/dr-m-dyson-wants-bring-more-investment-malaysia

UTRAJAYA: The Prime Minister, Tun Dr Mahathir Mohamad, has admitted that he has not received any information on allegations linking Lynas Corporation Ltd (Lynas) to withdraw this investment in Malaysia.
"I have never heard about it, they have never met me or the Cabinet," he told a press conference after chairing the Cabinet Special Committee on Anti-Corruption (JKKMAR) meeting here today.
A few days ago, Australia's High Commissioner in Malaysia Andrew Goledzinowski informed that Lynas's failure to operate might cause Australian giants to overrule the desire to invest in the company.
According to him, the plant is a pioneer investment for Australia in Malaysia.
"Lynas is very important to us as it benefits both Malaysia and Australia," he said.

How could Dr Matathir move from a historical position of support for Lynas to opposition?

To me the only issue to be resolved is disposal of residues, and we are told Lynas has a very effective plan to achieve this objective, the Condisoil project.

Suggestion to the investigation committee is to complete your investigation as quickly as possible and please ensure this review, as promised, will focus on disposal of residues and not turn into a witch hunt into historical approvals for establishment of the LAMP in Malaysia.