May God rest his soul.
It is interesting to read these words on the SSPX site announcing his death:
"...the Institut Sancta Maria, in Wangs, Switzerland, where he was able to spend his last years with the profound joy of shepherding souls."
Yet we were assured, as a senior priest of the SSPX confirmed to me, that he was retiring to the SSPX just to spend his last years in prayer and recollection and would not be involved in the apostolate.
It is gradualism in the SSPX. That is how the revolution triumphs by nullifying resistance.