Firstly, the facts as they currently are don't exactly portray Trudeau in a positive light. Lax border security makes it very easy for nefarious actors to commit acts like this. Lax border security seems to have been a factor here, because the alleged killers of Nijjar entered the country on student visas. If Trudeau were seriously concerned about foreign actors killing our citizens, we would have much stricter border security and a foreign agent registry by now, yet we don't have these things. Trudeau is abdicating his own responsibility to defend our national security, which makes me roll my eyes when he expresses indignation toward the Indian government regarding the killing.
It appears the Indian government paid the "students" after they had arrived in Canada. These types of assassinations also happen in many countries with famously tight security. If not through "students", the hit could have been conducted in any other way. So, while border security could be tighter, I'm not sure that blaming this on immigration policy is quite accurate.
It's also very suspicious that the Conservatives were reluctant to expand the scope of the inquiry into foreign interference to cover all actions by all foreign powers. Could it be connected to CSIS investigating Indian interference in the Conservative campaign in last year's Oxford by-election? I guess that explains Pierre Poilevre's BS-ing on this matter: he refuses to obtain a security clearance to review top-secret intelligence, because he would rather continue BS-ing than know the full facts.
Secondly, publicly accusing a state of killing your citizen is not a decision to be made lightly. It's better to know you will have backing from other allies as well as to make sure you have somewhat complete information. There's still a lot we don't know about the level at which the Indian government was involved - was it just a rogue intel agent, or was it ordered at the executive level? If it was the former, for all we know, Ottawa could have informed the Indian government privately and they might have dealt with the rogue individual. The US could also have privately intervened to side with Canada. If Trudeau planned to go public about the allegation, how it is revealed could have been co-ordinated with the US and other allies. He lost a lot of leverage by trying to be self-righteous and recklessly revealing the allegation on his own. Early in the dispute, the US seemed to side with Canada but didn't want to discuss it publicly, making the whole thing harder to solve. The reckless manner in which the allegation was revealed also made Canada susceptible to propaganda from Indian media, which also didn't help the situation.
Trudeau could have handled the whole thing far more prudently.
The PMO wanted to keep the story quiet, until Robert Fife approached it for comment. After that, it became impossible to cover up the story. It's the cost of freedom of press.
"The government refrains from commenting on ongoing criminal investigations." Obviously it was an ongoing criminal investigation, because they're just now making arrests. The Trudeau government has hardly had trouble during its time in power not telling the press anything, it's not like they have some grand commitment to transparency to where "we have to be open in public on this".
These guys were pretty dumb to stick around in Canada in my opinion.