How to setup Adroid Chrome to translate highlighted text via the pop-up Google search
Open Google Translate's settings.
Select "Tap to Translate", then enable "Enable".
In Preferred languages, set "Your primary language" and "Language you translate the most".
Go back to Chrome, select a word, "Translate" should appear. Click on it to translate the word.


Update

Based on Vadim's comment that the method might no longer work, to get the translation back:


Enter chrome://flags on your search bar
Type translation on the Search flag box
Set Contextual Search translations to Enabled.
Then Relaunch Chrome


You should be able again to see the translation at the bottom after selecting a word as seen on the image below.



Remarks:


Touch to Search must be enabled in Chrome's settings (Settings -> Sync and Google services -> Touch to search)
There are times when it stops working. You need either:

a. pressing the 3-dot then Translate or

b. to restart Chrome, or