I think you are missing that type="probs" should be set on the predict function call.
Like in this example I made:
library(nnet)
set.seed(42)
irispart <- slice_sample(group_by(iris,Species),
n = 5)
irismod <- multinom(Species~ Petal.Length , data=irispart)
predicted_obj <- as_tibble(predict(irismod, newdata = irispart,type = "probs"))
library(tidyverse)
(predicted_obj <- mutate_all(predicted_obj,
~round(100*.,digits = 2)))
# A tibble: 15 x 3
# setosa versicolor virginica
# <dbl> <dbl> <dbl>
# 1 99.8 0.19 0
# 2 99.9 0.08 0
# 3 99.9 0.12 0
# 4 98.9 1.09 0
# 5 99.8 0.19 0
# 6 0.08 99.7 0.23
# 7 0.5 99.5 0
# 8 0.32 99.7 0
# 9 0.03 93.6 6.35
# 10 0.03 93.6 6.35
# 11 0 0 100
# 12 0 0 100
# 13 0 0 100
# 14 0 0.32 99.7
# 15 0 8.56 91.4