A lot of Sikh separatists (who want a separate country from India) seem to have roots in Canada. The attack against an Indian plane a few years ago is probably the most obvious example. In addition, when Justin Trudeau visited India, he invited a separatist to have lunch with him.
There has been a relatively significant Sikh population in Canada over the past several decades, and the whole range of Sikh political thought is represented in Canada.
Subsequent to the attack on the Golden Temple (Operation Blue Star) and the assassination of Indira Ghandi by her Sikh bodyguards, there was a heightened degree of suspicion on Sikhs in India. This caused Sikhs who were affiliated with separatist groups, as well as Sikhs who thought they might be treated like they were affiliated with separatist groups, to want to leave.
The increased suspicion of Sikhs in India even let to the arrest of future Canadian Minister of Natural resources Amarjeet Sohi, who hasn't credibly been accused of any ties to militants.
As for the invitation of Jaspal Attwal to India, there's no sure answer to that, but there have long been credible voices such as former BC Premier and federal Minister of Health Ujjal Dosanjh who have suggested that the federal Liberal Party is generally more accommodating of Sikh separatists than they should be, however there are a variety of alternative explanations for why this happened.