My impression was that Botwinnik made a poor showing at the regular Soviet championship that the absolute championship, which was in a format that suited Botvinnik beter, was organised to let Botvinnik reclaim his number one spot in Soviet chess.

After the death of Alekhine there were 2 scenarios:

1) Give the title back to Euwe as last living ex-worldchampion
2) a match tournament

A vital moment was Groningen 1946; Botvinnik succeeded in becoming first, half a point before Euwe which strengthed his position.