John often writes as if 'what will be' 'already is'. The other gospels offer a more present tense message that looks forward to what will be.
For God did not send the Son into the world to judge the world 3:13
and He gave Him authority to execute judgment, because He is the Son
of Man 5:27
Obviously this judgement would commence at a later time, but John writes as if Jesus has already supremely accomplished his mission and the next stages are already unfolding.
Jesus fully understood what his mission was under the loving and righteous hand of his Father and God. He understood the glory that would be his and how he would glorify the Father when he succeeded the final test. He knew that he would be given great authority and nothing would be left outside of his domain.
The 'all things' are that prize of doing the Father's will against all power to draw him into sin. No doubt, this buoyed Jesus as he faced every temptation and bowed to the Father's will on every occasion - even if he did waver at the final hours before a terrifying death.
This is nothing to do with Jesus being God. If he was God, he wouldn't need to 'inherit all things' as they were already his!
Heb 1:2 ‘in these last days has spoken to us in His Son, whom He appointed heir of all things, through whom also He made the world’ (no, he didn't make the world, it should be 'ages'. Just as he wasn't 'returning' to the Father, as he was never IN 'heaven' to begin with)
That he was 'appointed' heir, speaks volumes of his subordinate relationship with God, as do many other texts that how Jesus is certainly not = with the Father/God.
Got to watch out for all those added/mistranslated words