How to compile the 5.x kernel tree without exploding ten times against Debians 4.x

I am a fairly experienced kernel compiler – BUT honestly I started with version 5.x, each module is about 10 times bigger
than the modules provided with debian 9.x.
I usually do it in two different aproches ::

  1. make oldconfig -> make menuconfig (add something new som) ->
    make -> make modules-install make install. OR::
  2. make allmodules -> make -> make modules_install ->
    have it installed.

With the 5.x (and maybe 4.x either)
all modules (and initrd) are inflated ::

initrd 4.9.0-8-amd64 26 241k <> 5.0.4 366 163 k
for example: drivers / memstick / core:
memstick.ko 4.9.0-8 27 252 <> 5.0.4 375 496

The above examples are representative of all modules.

Sorry, but I've never had that kind of problem.

What am I doing wrong ???

Please help