That analysis was done by a group of individuals with strong ties to the biggest opposition party in Estonia, whose voters are primarily those who are less likely to participate in e-voting; they've been anti-promoting the e-voting system ever since they went to opposition; prior to that, they'd been openly positive about it it.

The analysts themselves were invited to the country and to do the analysis by that opposition party (Centre Party/Keskerakond); they had participated in several Centre Party events prior to publishing the research. They were reimbursed for their expenses and most likely paid a fee for the analysis. The group had demands that the system be taken down; they however refused to publish details about the study which is uncommon and is not a sign of goodwill.