The key to success, according to the parable, is cultivation.
Lack of removing stones was the downfall of some. Lack of removing weeds was the downfall of others, who, initially, had no stones to hinder their growth. But the weeds had not been removed and they competed : a competitive form of life to the word.
The wayside had no cultivation at all and therefore was an unsuitable place for seed to fall. It was wasted. The enemy (birds or Satan) had access and the seed lay unprotected in an infertile area.
There had been no preparation. No clearance, no digging. Nothing could go grow there.
It was uncultivated.
The initial chapters of all four gospel accounts clearly express the importance of a preparative work (prior to the sowing of the word) which work will ready the heart for the reception of the word.
If one has had no thought of death, of eternity, of one's own sinful state, of the brevity of life, of the necessity of judgment, of one's own committed sins - in thought and word and deed - then the word will be meaningless. No cultivation.
It is clear from the gospel accounts and the epistles and the book of Revelation that the Wicked One, Satan, Diabolos, the Serpent, the Drakon - that that entity has ready access, through the world and worldliness and the lust of the world ; and through the flesh and its desires and its proclivities and its lusts ; and through the effects of nature and natural relationships, through all these means he can influence the soul.
Unless it has been cultivated, otherwise.
For thus saith the LORD to the men of Judah and Jerusalem, Break up your fallow ground, and sow not among thorns. [Jeremiah 4:3. KJV]
Spiritual exercise, penitence, moderation in natural things, carefulness in regard to the flesh, circumspect behaviour in regard to relationships : all is necessary if one is to benefit from the word of God.
Otherwise, it is immediately plucked away.
The heart has no grasp on it. No affinity. The heart will pulse after that which is vital. It will not engage with that which it does not recognise. Survival depends on priorities. And what is uppermost (as the heart sees things) is that which will receive prime attention.
'The heart is deceitful above all things and desperately wicked : who can know it ?' Jeremiah 17:9. It requires a powerful work of the Holy Spirit to break it up, to break it down, to make it malleable, to render it receptive.
Otherwise, it simply does what nature does : eat and drink and marry and give in marriage . . . . until the Flood (of judgment) comes, Matthew 24:38.
No cultivation : no penetration.
And thus . . . no fruit.